Can’t remember right off, but the change from Leaded fuel to unleaded happened about the time that unit was made, and I think it’s a leaded model. If so burning unleaded will cause the engine valves to wear faster. You will need to run a lead substitute in each tank of gas you use. The other alternative is to have new valve guides and valves installed so you can run unleaded.
The water damage can be fixed but it will be time consuming. And you may have to take the siding off to replace frame work. It will be a big project, but if you have the skills and determination to get it done, you will have a RV that you can be very proud of.