Campers haven't changed all that much in the past 30 years other than getting slides and updated appliances with more electronic controls.
The basic build structure is mostly unchanged. The sealants and caulks have improved over the years but the basic design is little changed.
You will have the inherent issue of water intrusion on an old camper. How much intrusion and the resulting rot is entirely dependent on how well the original owner too care of the seals and caulk, but even if they did, I would fully expect some.
I've posted this before on here and other forums and it bears repeating again in this case. You need to look closely to see if, in fact you have an under the outer skin rot issue. You need to lift the mattress and look under the front of the mattress in the nose for signs of discoloration which means there is water intrusion and damage. Look in the cabinets if there are any against the nose, look in the lower outside corners. Look under the sink along the base of the inner wall and inside any cabinets where you can see the inner wall, where it meets the floor line. If you see any staining, it means it's gotten wet and most likely, the frame is rotting and producing mold (many forms are toxic) and will need to be fixed, which is a simple but very time consuming job. In extreme cases of advanced rot, you can easily pull the tie downs out of the camper, because there is no wood to hold them. Another sure sign of rot and intrusion is sagging where the jacks attach to the camper. Rotten wood won't support the weight of the camper, so the camper side sags on the jacks.
With a camper of that vintage, you will certainly have some rot issues, but the mechanical aspects, fridge, stove, plumbinng, furnace and waste systems are basically unchanged.