I can't say about the rest of the coach, but the 5.9 is a decent little engine, BUT 1998 was the first year with the VP44 injection pump and they are good provided you make sure the lift pump is providing enough fuel. The stock lift pumps are a known weakness on these engines. The engine will run (for a while) when the lift pump quits and what happens is the VP44 gets hot and it will gall the timing piston and bore causing it to stick. The only repair is replacement of both pumps. It also sounds like someone over heated or melted down the engine to need the parts that were put in. These engines are designed to run about 500k miles before rebuilding.
2005 Dodge Ram Four Door Dually Southern Comfort Conversion
2017 Forest River 365RK