You have to purchase a digital ready HDTV like the LCDs from WALMART... We originally got two 22-inch flatscreens from WALMART back in 2009 ($150 each Holiday sale) when the change-over came about.
If you plan on mounting the flatscreen using a swing out mount these can be purchased at WALMART as well. Be aware the RV walls are very thin 1/4-inch wood panels and a screw will pull right thru them. Needs to be mounted to a back board which some location have theses already built-in for you or you can add one yourself on the outside of the thin wall and paint to match your decor. You need at least a 3/4-inch back board. Then you can use regular wood screws for the swing out mounts.
Our first install used something like this google images shows...

Even the larger HDTV will have to be moved out some to get to the connections in the back or remove it if you want to store it or take it down for the road trips like some folks do. Abandoning the large hole the old analog TV was at gives you book case or other similar installing. Maybe mount the HDTV on a swing our a door or something???
The flatscreen do not weigh anything like the old analog tv's do... Our 22-inch flatscreen weighs less than 40lbs
We also purchased 120VAC models and when we want to run them when camping off grid we use a small wattage PSW Power Inverter.
Roy Ken