We have such a setup on our 05 Wildwood TT. We bought a 19" Samsung flat screen with 720p and mounted it with a swivel mount on the side of the kitchen cabinet. I have a posting about this somewhere on this site from when we did it, as the mount was the real issue, and it worked great. Walmart sells a similar mount for $50 that would also work well. We pipe the sound from the headphone jack on the Samsung into the built-in AM/FM/CD/cassette unit which in turn pipes it to all the speakers throughout the trailer, including the outside one. THIS SETUP WORKS GREAT. You set the console stereo on AUX and then dial up the volume and away you go. The AUX input connectors, if memory serves me, are located behind the stereo unit with the wiring harness.
We DID NOT buy a combo unit with DVD, because the clerk disrecommended them, saying that they had a lot of returns and a lot of problems. Instead, we use our daughter's Playstation 2 (a PS 3 is better - you can do BluRay movies with it) as our DVD player. It's a bit of clutter at movie time, but not a big problem really, and we leave the PS2 in the trailer for the kids anyway, so they can play games with it. Two birds one stone.
The nice thing about the Samsung is that the built-in sound is excellent (without being plugged into the console stereo) and the receiver in the TV is great, too, so we pick up lots of digital over the air HD channels even though we are in the deep woods. We get like 30 channels, and most have a crystal clear picture. However, we also bought the Wingman accessory for our antenna, which made our good reception even better.