As a fellow former boater I can assure you that the transition to RV'ing will be an easy one. The plumbing, electrical etc. are all about the same and perhaps... a little cheaper.
I would not recommend buying new, especially at a show. You will pay far too much for what in all probability will not be your last coach. You will lose 35 - 40 percent when you dirve that new rig off of the showroom floor.
There are lots of great deals out there to be had on lightly used units. Go to the show {but leave your checkbook at home... seriously!} Find what you like, floorplans are critical and then go steal one on the used market, NOT from an RV dealer.
You will have a far better chance of getting what you want/need the first time and will save more money than you can imagine. In some states like Arizona, there is no sales tax on private party sales. Best of luck and if you would like a little more info from a fellow former boater {40 years} feel free to send me a PM.
:C