Husband going for initial neurology appointment Monday. What can I expect?

Having voiced my concern to his PCP about behavior changes, short term memory loss, inability to focus or concentrate, etc. his doctor did a cognitive test in-office and DH did not do well. All our local neurologists are booked very far out. The PCP found him an appointment at a very reputable teaching hospital about 45 minutes from our home. Every day I notice my DH getting worse. He is a lifelong mechanic and can do/fix anything....in the house, cars, RV's, appliances, plumbing, electric, etc. We recently had our bathroom painted and I had bought all new towel bars. My husband has put in towel bars before, without any issue or help. He opened the first towel bar and was just looking at one of the end braces...totally confused and unable to figure out how it gets installed (standard towel bar...nothing different), turning it over in his hands, just befuddled. So I stepped in and helped him figure it out, helped him hang the towel bar, which I never had to do before. We only got 2 hung that day, then 2 more the next day. Simple things take him much longer. I see things everyday that he seems to be struggling with. His thought process has become much slower. He is 67 years old. I am 58. We have been married 5 years, together 7. He denies that anything is wrong.

My questions are - What can I expect (tests, etc.) during the diagnosis process? How long does it take to get a diagnosis from the time of the first appointment with the neurologist? I know that SOMETHING is wrong...just don't know what yet. His B12 and D levels were both "low normal" and his testosterone is fluctuating wildly (between 300 and 1300, up and down, over the course of a couple years) so his PCP wants him to see an endocrinologist (tomorrow). However, his PCP told me he believes DH's problem is neurological. It just scares me to see my DH seemingly getting worse every day. Looking back, I see that he has had symptoms for several years and I never, ever equated them with cognitive issues.