Does your Jensen work off 12v now? The 12V TV selection is going to be narrow for you as most of the better ones are 120v. If you find one with a 12v wall wart, you can wire it directly to 12v. I run my Toshiba and Panasonic TV's off a 300w Pure Sign Wave Inverter when necessary.
As to the mounts, the mfg's do funny things. On my new Rockwood Windjammer, I could not for the life of me figure out how the TV came off the wall as you really couldn't see behind it, and there were no latches, etc, to lift or swing it out. I had to email Forest River to get the answer. They attach a an aluminum plate to the back of the TV with slotted holes. You have to lift the TV up and and it releases of of pegs. Works quite well actually once you see how it works.