Go to an RV show. This is the time of year they are on. Find one in your area and start looking there. This will give you a great idea of what you want, what you need, and what you can buy.
Once you find what you want, get the specifications (weights and such) so you can be sure you have enough truck to pull it. If you already have the truck, get the specs for that, and make sure you don't get a 5th wheel beyond those specs.
Oh by the way...WELCOME!