The obvious answer is to make sure you have an HD source. The new standard requires all TVs to support ATSC, which is digital--not to be assumed to be HD. Most of the channels have moved to the UHF band. Your old TV antenna will work, assuming it's like most RV antennas. Although it will work, it may not bring in distant stations or some channels in the UHF band. You should upgrade or replace your rooftop antenna to support digital TV. You'll likely upgrade your DVD player, if not already an HD variant. This will result in choices on how to hook it up to your TV. Use the HDMI interface it all possible. The picture will be the best it can be and there's less cabling. If you can't use HDMI, use the 5 cable hookup (3 picture and 2 audio). If you have SatTV, make sure you have a HD receiver, HD capable satellite system, and the HD subscription.
Other than carpentry work, the physical installation should not be too hard. Cabling can be the killer. I just moved my HDTV Sat Receiver, DVD, and surround system from the front of the coach to the shelf just above the large mid coach TV. Although I had to be a bit creative, I was able to re-purpose all existing cables. I looked at running new cables and it looked too difficult given the alternative. It can be done, but not overhead.
Best of luck,
Gil
