I took my new-to-me motor home in for service after owning it for a year. A small leak had developed in the black water slide valve. I figured I would have them replace both black and gray valves since they are right there in front of you with 4 bolts holding them on. Parts are about 30 dollars. He quoted me 360 dollars to do it with 3 hours of work time! Am I missing something? It looks like an easy job to me. BTW he also is charging me 220 dollars to "service" the roof which I think means washing it with a pressure washer and spraying some preservative on it. I would appreciate your thoughts!