Are there any resources or helpful hints for making a house wheelchair accessible?

Whichever door the chair fits through would be best to make wheelchair adjustments for. If both doors work, then the access that has the least number of steps with area in the yard to accommodate a ramp that may have 1-2 turns is probably the best to use. Make sure that the ramp has side rails and that the floor of the ramp has non-skid surface. You can rent ramps or ask a reliable contractor to build a ramp out of wood or buy ramps from local home improvement stores. Steepest slope is 1 inch of rise (up-down) for 12 inches of horizontal (side to side) length.

I have a couple of thoughts on this.

1.  There is a home near me where it's a straight ramp from the front door all the way to the sidewalk and after that it's a 5-lane busy street.  There's nothing to slow down a runaway wheelchair.  I'd recommend a zig or zag in the planning. 

2.    The permanent ramps I found were into the thousands to construct and would take time to build.  Since we were not at all sure how long elder would even be able to stay at the home, we worried that the ramp wouldn't even be built in time for her to use it, so you might want to consider that aspect.

3.  We did find another company and arranged a ramp rental.  The guy came out, measured, and then went to his warehouse to get the sections he would need for our specific design and simply put them together for us.   We liked it because it did not take long to get it and it was not permanently attached to the house in any way, so it was easily removed with no damage to the house.    If you're not sure how long you will need the ramp, you could look at a rental.   I do not think we needed a permit for this sort of thing, but you should probably check.

Look up 'ramps for elderly disabled' on the internet. There are groups who do this sort of thing for free or very little in payment. Some church groups have people who do it as a mission.

The portable ramps, if you can afford them, are quite good. Depending on how high it is from ground level to door entry will determine how long your ramp needs to be. To be safe, the incline cannot be too steep or walking person would easily lose control. Sometimes you will even need to have a ramp that zig zags where you make a turn to prevent the incline from being too steep.

If you have a community website, like NextDoor (check internet), there are lots of people who have the skills to do a wooden ramp for you and tend to be pretty reasonable helping a neighbor.

There are portable ramps. I have one that allowed me to have a ramp built in the garage. A platform from the door, a ram off to the side then another platform. I put the portable ramp on that. When it is not being used I fold the ramp up and store it on it's side. the platform is the height of a step so it works well.
The other thing you can get are hinges that you can put on doors that she uses. The full swing hinge allows the door to open about another 1 to 2 inches so there is more clearance.
the other obvious things, remove carpeting if possible. Area rugs are also a problem. Both are hard to wheel over.
Check with your local Senior Center some have volunteers that will build ramps.
Often you can find used portable ramps on the FB garage sale in your town.
Depending on where you live if there is a rural area some farm stores have ramps but they are easy to find on line. Do a search for portable ramp. All you have to do is put in the height and it will calculate the length of ramp you need to comply with codes. (I ended up getting a shorter ramp since I was going to be pushing and I felt that I could handle the weight/height/distance)
If you have a permanent ramp built check with your local village or county you may need a permit and it will have to comply with ADA codes. (this can make a ramp VERY long.)

Thank you so much! I have been overwhelmed trying to figure out where to start, you are a hero. We are in california, and our weather ranges from intense heat to yearly snowfall, and everything in between. We do not have a garage, but our front porch is covered. It's not very big, but could provide some coverage for getting in and out of the door, at least. But our car access is in the back, and if we made the front the main access we would have to figure out how to take a wheelchair over a gravel pathway and over a curb

1.    Where is your GM located?  I.e., in a southern or winter state, or in a state that's typically southern but like Texas became a winter state overnight?    I ask b/c if you're in a winter state, and if there is an attached garage, you might consider that as the entrance and exit.  It would be much safer not only in winter but during rain or windy weather.    

2.    I've seen various ramps at the apparently now defunct AAA expos, and gathered literature from the contractors who installed ramps.    Given the pandemic, I'm not sure how many of them survived though.

So I'd search using these various parameters   (I just started search after injuring my back; these are some subjects and linked to potential resources):

Aging in place, ramps
Senior (or elderly) resources
Entrance and exit safety with ramps
Elder care, safe exit and entrance

Adaptive contractors
Special needs and disability contractors
ADA compliant contracting (or adaptation)

See more at:

https://www.google.com/search?source=hp&ei=O3YxYOGnNpjatQat2KvYCQ&iflsig=AINFCbYAAAAAYDGES_FDjWHwLgfqoN90ZO2PiGCb9zeK&q=adaptive+contractors&oq=adaptive+contractors&gs_lcp=Cgdnd3Mtd2l6EAMyBQghEKABOggIABCxAxCDAToFCC4QsQM6CwguELEDEMcBEKMCOggILhCxAxCDAToICC4QxwEQowI6DgguELEDEIMBEMcBEKMCOg4ILhCxAxDHARCjAhCTAjoFCAAQsQM6AggAOgsILhCxAxCDARCTAjoICC4QxwEQrwE6AgguOggILhCxAxCTAjoKCC4QsQMQChCTAjoHCAAQsQMQCjoLCC4QxwEQrwEQkwI6BggAEBYQHjoHCCEQChCgAVD2BVjJGWDvGmgAcAB4AIABcYgB0wuSAQQxNi4zmAEAoAEBqgEHZ3dzLXdpeg&sclient=gws-wiz&ved=0ahUKEwihse3Sq_nuAhUYbc0KHS3sCpsQ4dUDCAw&uact=5#spf=1613854272570

https://aginginplace.org/creative-exterior-modifications-for-effectively-aging-in-place/ (good source, with advice on lighting and more)

https://aginginplace.org/5-ways-to-make-your-entryway-safer/ (entryways)

https://www.seniorly.com/resources/articles/top-10-home-modifications-for-seniors-staying-home  (more general, and less specific, but some good topics for a checklist)

https://eldercare.acl.gov/public/resources/factsheets/home_modifications.aspx ; (links to other sources)

You could also contact your local Senior Center, county government's elder division, and state's elder resources (if your state has them)

3.  Have grab bars installed by a certified carpenter, into the studs, around the house, and at entrance to internal and external doors.   Remove potential blockages of furniture, throw rugs, etc from the interior of the home.

4.  I saw a woman using a ramp from the ground to cargo area of an SUV, and reversed.   She  had a daughter who needed wheelchair exit from the vehicle,
and the ramp provided what I thought was a good option.   Someone would need to be available to guide the wheelchair though.

5.  A home in my neighborhood has a lift in front; it was created years ago.   There's a "booth", like a telephone booth, which I believe hosts the wheelchair lift.   I've never seen it operated, but I think the wheelchair is either rolled from the porch, or from the sidewalk, onto the lift, which is then mechanically raised up or down to the porch or sidewalk level.   This might be more expensive though.

6.   Financing:   If your Senior Center has a social worker, that could be a good source.   AAA is another, as are the local community, county and state government elder divisions.   Some communities used to get HUD funds at the beginning of each fiscal year for emergency adaptations for residents.  I don't know though whether those kinds of funds are still available.

Habitat for Humanity, Christmas in April, and some Methodist Churches may be able to offer assistance, with their volunteers.  

BTW, I'd also search through DuckDuckGo as opposed to Google, unless you want a lot of contractor ads.  DDG doesn't follow users online, so your searches aren't monetrized as those used through Google.