Dear Jackcat, of course you should do whatever you need to do for a happy future. If that means selling the Airstream, then I wish you a quick sale to a good new owner.
On the other hand, I still work, and am long unmarried, so as a single female it isn't easy to take long trips. I've found that there are dozens of wonderful places to visit and camp within 100 miles or less of my home base - and a few others under 300 miles from home. If that kind of radius is doable for you both consider it.
I highly recommend that you try to get MRS. Jackcat behind the wheel of the big truck and towing the Airstream. If that might result in murder consider contacting a truck driving school that runs a RV towing course. Many do. You could always rent a little utility trailer for your wife to start out with if she's fearful. You might also decide that shorter trips could mean a smaller trailer, and I'll bet there are dozens of people in forumland who might just want a bigger rig. Trade?? Why not?
You might be limited by needing to be near to a medical center, but in today's world you can have all of your medical records on a flash drive or a laptop... and you could travel farther than you think possible. That of course is between you and your doctor.
Doctors... Hmm. Well they give advice on how to keep your body going and going and going and going... But we are all really GOING to end some day.
I imagine going to room temperature in my Airstream might seriously impact it's resale value... but screw it, I won't be around to spend the money!
If traveling and camping will not be fun or comfortable, I hope you find a beautiful place to retire and enjoy. There are some beautiful places in Arizona and New Mexico. Happy trails and happy landings.
Today is a gift, that's why they call it the present.