If it doesn't leak, even if the electrical and plumbing are not usable it will provide you with a mobile "tent" that keeps you off the ground.
Friends get plenty of use with their popups whether or not they are using the plumbing and electric systems. If the refrig works, that is a bonus.
Big thing is that the canvas is in good shape and doesn't leak. Then make sure the main roof is in good shape, AND that the raising and lowering system works dependably! If you can't raise, and then lower, the "popup" than it is not usable.
You may want to replace the foam beds.
A 1976 popup? That's just about 40 years old. If it is in excellent condition, then great, but just be careful with it!
