The photo of the 40 year old camper makes it appear to be in good shape. Get some cleaner to remove the black steaks and it would look new. What parts of it need to be redone? I had a friend in Colorado with one of these and his only comment that I can remember was how heavy a camper it was. Of course, this was back in the days of a 3/4 ton pickup with factory suspension was considered to be a "big" truck.
I had a set of those removable three jacks, two on one side and one on the other. They were scary to use to load and unload. The first thing I would do to that rig is install a set of good electric jacks on each corner. LOL
Sounds like a fun project, especially if you have someplace to work on it indoors.