Personally, I've found that you can get a better deal at the dealership than at the show. Very few people like to haggle and find it difficult to do. Consequently, you often get bad info about where the best deal can be had because aren't willing to admit they didn't negotiate well.
Do your homework and compare prices. Keep in mind that you really ruin a negotiation by coming in with some ridiculous pricing or pound your chest like your some big negotiator. Be pleasant and firm and you'll get a good deal. No your prices and be REALISTIC about what your trade in is worth to a dealer who has to make a profit on it when he sells it.
Lastly......I think you're buying a little early for retirement. A lot of things will change in five years when you retire. For one, your warranty on the engine and trans will be expiring just as you hit he road to full time. I would buy a used interim RV and then buy your retirement coach about a year out. Just too many things can change in five years from RV design and amenities to your personal health and family situations. We bought our first DP 5 years before we retired. It worked out okay, but as I look back, it would have been better to buy about a year before. Motor homes and our needs had changed. Just my opinion.