e-man makes some good point. Our Sunnybrook was fiberglas over an aluminum frame and had much less trouble with it that we did with the Terry that had a wood frame. The quick connect "rinse port" is basically a garden nozzle with a coiled hose as opposed to a traditional shower head. The premise is that most folks use the outside shower to rinse things off rather than take an actual shower. We find it nice for rinsing the sand off at the beach.
According to the specs your Grand Design will have 30A service, which is all you need for one a/c in that size TT.
Also good point about the heat ducts in the walls and cabinets. Our Terry had them in the floor and it's impossible to keep stuff from falling there especially when you sweep. They're not even ducts, more like thin flashing lining a joist bay.
If you have the dealer holding the Grand Design, I would do all of your research ahead of time and be ready to pull the trigger if you like it.