Everyone does things in a different way. If it were me,,, I would fix the leak in the roof in the easiest way. Fix the damage inside to look nice. (Painting might be involved.) And run it. You said you are only going to use it occasionally . Why spend a lot of money and time on it? Make it work in the easiest way that best suits your needs. Camping is no fun if it involves a lot of restoration work just to get to the spot occasionally.
Remember I'm a Caveman I do things differently then a lot of people. (And have a lot of fun while a lot of people are spending money, and effort on little things.)