A 2000 gas RV with only 5500 miles on it. Yikes. And not driven the last 7 years.
Really, it should have around 50,000 miles. Reason you might want that mileage is because a gas engine that just sits, develops issues with many of the rotating parts internally. For instance, the ball bearings supporting the crank shaft can develop a flat spot where the weight of the shaft rests. When you start the engine again and run it a while, that flat spot causes the bearing to go bad. And as you can imagine, there are many rotating parts. So be prepared to remove the engine for an overhaul...
The good news is that if conditions were right, modern engines can last unused longer than older engines and I'd think a MY 2000 might be one of those. Mostly sealed, using modern oils and antifreeze, etc.
Good luck!