Mary, my heart goes out to you. My MIL was a hard-headed independent woman who outlived 2 husbands. She lived in the top apartment of a 2-story building for 20+ years and didn't want to move. Your MIL may be in decent health for her age but I'm sure it's already crossed your mind that it could change at any time.
My ex and I dealt with his Mom for seven years and she had a similar attitude to your MIL. So I have a strong suggestion, if you and your husband are expecting to have little or no help from the rest of his family, he will probably end up being her guardian. The person he hires, the live-in for MIL will, I expect also be asked to watch over her and report to him with problems, concerns, etc. If this is the situation that is beginning or looming for the near future, then you might want to consider moving her closer to you. She's not going to like what you do and you already know you can't please her, so you will want to find a balance between her care and your sanity.
My mom's gone 2 years now and my sister, who was closest to her both geographically and emotionally during the last few years of mom's life was in charge of dealing with doc appts and meds. My mom wasn't quite as stubborn as my MIL but she had her down times when she didn't like having to be taken care of, recognized and hated her impending loss of independence. My sister finally told mom that she was now in the time of her life when roles need to be reversed. The elderly become the children and their children become their parents, so to speak. Maybe that argument or something similar would help your MIL calm down or at least begrudgingly let you and your husband do what needs to be done.
Also, if this is the first time you're helping an elderly parent, even one who is understanding and cooperative, dealing with any health care system that focuses on the elderly, even the best of them, are an experience in itself. As the others have mentioned, there are plenty of horror stories (I have a few myself) and you may not be able to avoid working thru one before finding what works best for your MIL and that you two also like.
Mary, I don't know you and your husband at all but I was in your shoes about 10 years ago and learned that this process of taking care of the elderly can be very challenging on a marriage. Many times I didn't agree with my his decisions and he knew it. It's a tough spot for a husband/son, wife/daughter-in-law to be in and work thru.
If you'd like to talk and/or share further, please don't hesitate to PM me.