With that truck I wouldn't be getting a hard sided trailer more than 4000 lbs. the wind will move your truck and trailer around quite a bit, you will want some sort of anti-sway set up. Plus, once you add in gear, all the womenz stuff like food and cooking materials and extra clothes and blankets and toys for kids and dog accessories etc, you will add up a good bit of weight.
plus, figure a 30 gallon fresh water tank, that's another 250lbs, if you have anything in the grey or black, you are pulling more. When you get one and go, find a spot to fill up water near your camping area or if they have a fresh water hookup don't out any in the tank. Saves a lot of weight. and dump after you camp if you can find somewhere close.

you will want to get a brake controller installed. That truck will be severely handicapped without getting one. Think a full camper going down I-70 on the back side of Eisenhower.

dealers are really just for looking at IMO. campers on average probably get used 10-20 nights per year. Even a 10 year old camper has seen very little use generally.