Lee-- Watch that they don't use to much pressure on the roof or the sides of the Monte. The pressure they use at those truck washs are really some high pressure units. Besides possible damage to the roof, it could also blow off or loosen your decals! I'd also warn them not to use the pressure directly at the slide opening! I've seen where water can be blown in past the gaskets on the slides if not careful!
Let us know how things turn out!