I found out Mom doesn't have Medicare for prescriptions and her surgery was less than 24hrs away. Which Medicare Part C do I chose?

After surgery medications such as vicoden are not very expensive and one of the discount pharmacies should have something suitable.
As far as a medicare supplement plan is concerned I have a Blue Cross PPO which costs (next year) $108 a month and that picks up the 80% Medicare does not cover plus medications with low co-pays for generics.
You need to get on with the application because we are in the middle of open enrolement. call the various companies that serve your area and they may send a representative to your home. Mom may have to pay a small premium because she did not elect for part D when she signed up for Medicare. some area have eldercare advisors who can walk you through the minefield. if Mom is very low income she may also qualify for Medicaid so ask about that too. I am not familiar with other major plans but I imagine they off similar coverage and competitive cost. Obamacare is likely to make many changes so you may think differently next year but coverage is essential for the coming year

Formularies, right answer

If you are just looking for a way to get your parents Rx's you don't have to join a HEALTH plan, you need to join a DRUG plan! Look at Medicare part D providers such as what I have with CVS/Caremark. To choose which drug plan is better you want to look at the online formulary of each company and see if it covers the medications your parents are currently taking it you know they are likely to take over the next year.
I choose the Medicare part D coverage (plan) without choosing a health plan, that way I am not stuck in an HMO and I can go to my local physician who is good, or drive an hour to the major medical center and see the docs who actually specialize in my conditions. It was a no brainer to me! It takes me an hour to get into the city, but it is SOO worth it in the end!
~Wheelie :-)

We use Blue Advantage without any problem. Prescription drug coverage is included in it. Humana and other companies have similar Advantage programs. The only thing to be careful of is if facilities you use are in the network of the advantage program you choose. We like Blue Advantage because it doesn't have a network. Most places that take Medicare take Blue Advantage.

I'm not sure what Medicare C even is. Medicare D is the prescription drug coverage that was developed under the last George Bush. It was a godsend to seniors!