Just thought I'd post a quick update, I realize it's been a couple months.
We had all of our issues fixed in one warranty claim. The fridge, which was not cooling properly on propane on hot days on the road turned out to be missing a shield that goes inside the vent, and there was no insulation around it to keep the cold in, either. The rims and tires were replaced with the proper size for originally stickered for by weight. The sewer tanks did prove to be plumbed backwards and that has also been re-done. For all those who were asking, it was all handled very well by Gulfstream. While of course I would have preferred to have it all correct to begin with, this thread sounds as though these things are pretty common, and I think they did a good job of handling it and following up on everything. Thanks for everyone's advice and comments - very helpful to a first time owner.