We have a '17 274DBH which is very similar to yours and we love it. I installed a 32" TV. I just swapped out our mattress topper and factory P.O.S. mattress with a full queen. There is only a 1/2" to spare by the doors, but it fit. Really you need to measure to make sure, that is all we did. You should unzip the cover and look at the factory P.O.S mattress, it is a joke!!
If this is your first camper....which ours was, you will be a little star struck. I missed a ton of stuff and so did the dealer on a brand new camper. They made good and fixed everything, but I had it for a week before I found everything. It was all quality build issues from the factory. Since you are traveling a distance you don't want to take it back for warranty repair.
1. Make sure all Appliances work. Our Water Heater worked on Electric, but would light and go out on LP. They had to replace the controller.
2. Look for build quality issues, Some have them some don't.
a) There were screws missing around some doors and windows.
b) Look at all the seams and seals for possible water entry. They missed that there was absolutely no seal around the water heater on the outside. Rain could run down the siding behind the water heater and right into the camper. (Probably why the controller failed)
c) Look at tanks under the Trailer. Our fresh water tank was installed crooked and they just crushed it between the floor and the mounting rails. Plus our black water flush hose was installed kinked off, so the flush wouldn't work.
Like I said, we love the camper and layout. Our dealer fixed everything under warranty, but just things to look for. I never thought I would have to find that type of stuff on a brand new camper!! Hopefully some of these suggestions will save you a trip back to the dealer.