You have a huge advantage over most folks. I've used Tricare Standard all over the country and never worried about going broke from medical bills. Don't forget the Tricare Dental for retirees either. Another added bonus is discounts for retired military. They seem to be everywhere now. The back of my credit card says "See Photo ID". When a cashier asks to see ID I present my military ID and frequently get surprised with a discount.
There are companies that specialize in fulltimer rv insurance. I'm currently insured by National Interstate. There are others. A previous poster suggested Gilbert RV Insurance - that's a good place to start getting quotes but you can also google it.