Welcome and congrats on the new rig!!!!
As mentioned, fuse/breaker panel is near the floor in the kitchen area most of the time. May have a fuse or two at the battery.
Tv brand is your choice. How much do you want to spend and what will fit? Reception may not be the best so I suggest a dvd player also....
Is there a spot for the radio and it was removed (what it sounds like)? The use of an aftermarket car radio may require some custom work to mount it. Or what about a decent bluetooth speaker if you have a smart phone/ipod/mp3 player??? Gives the choice of taking outside, down to the beach, around home use, etc....
Did you get a wdh with the tt? If not, highly suggest getting one. If so, regardless if you bought from a dealer or private owner, you should double check the wdh adjustment once you have the tt all loaded up for a trip. Dealer only sets up the hitch for an empty trailer, and if a private owner they had the wdh set up for their tv (tow vehicle), not yours.... Follow my signature links for a ton of wdh info if needed.
Is this your first tt? If so, make sure you have a good sewer hose kit (inspect it if you got one from a private owner, buy a bettering one if from a dealer starter kit), white fresh water hose, 30amp extension cord, 50amp make to 30amp female adapter, 15amp male to 30amp female adapter to plug in to cool the fridge (may not be enough to start the a/c though), boards/blocks for leveling the tt (I use 2x10's, others use the "lego blocks"), wheel chocks, possibly a surge/electrical protector, and I know I may be missing some stuff....
When running the fridge have the tt as level as possible, it is better for the fridge.
Don't hesitate to ask any questions!!!