Hi Julia, I'm sorry you're not able to enjoy your RV. I have a 1985 Toyota dolphin I've had since 1999. I got lucky when I bought it because now I know fuel injection and the one ton rear end are things I would not want to do without. For the money it is gonna cost to fix your 1982 Personally I would say I would sell it as is and put the money toward a newer model that already had the rear end done and was fuel injection. Some people highly value the all fiberglass bodies that the Sun Raiders have. But on my metal sides I've had no problems except having to seal the roof items(Vents etc.) every couple years because of all the movement. As a side note I am convinced to remove all screws from roof items and just glue the vents on except the AC to prevent leaks from forming.
I would recommend taking a mostly objective look at the whole picture and determine if the interior has issues like leaks wood rot appliances that don't work cushions that need recovering plumbing issues electrical issues Etc. And decide if a newer model Could solve some of the problems you have. One thing about buying a RV of this type where they are very old find a seller that is willing to let you have the engine examined by a professional that can take compression properly and other tests to confirm the power plant is sound. Also you're 82 may not have cab AC which I find is so necessary in the desert where I live 29 palms CA. So moving up to a Slightly newer model may have other advantages. Also you may find someone that wants a sunrader specifically for the fiberglass body that wants to put it on a 4 by 4 chassis and has tons of money to trick it out.
Sorry if this is not a solution you're hoping for but we really appreciate your post on this site because we are a Toyota community take care
Pete Wisda