I just completed my first flat screen conversion on my 2003 Ultimate Advantage 40e. The TV was located in the front center overhead cabinet. It was a 26" RCA. It was replaced with a 32" Emerson flat screen model no. LC320EM2 from Walmart. I removed and totally discarded (stored actually) the original oak surround. I used a Morryde TV mount, model TV40-001H. The new flat screen fit perfectly side to side. My cabinet floor was already sloped toward the viewing area, so I had to turn the TV mount mounting plate upside down to drop the TV far enough to make room for the OEM surround sound speaker mounted above the TV, and to set the right angle to match the angled cabinet sides. The biggest issue was the curved metal front on the bottom of the cabinet. After some consideration and trepidation, I unleashed the metal cutting tools and removed the curve, making the bottom front straight across. I originally intended to create top and bottom boards to match the original oak cabinetry, but after a couple of weeks dawdling the DW declared she liked the black look above and below (as seen with nothing filling the gaps ...she watches TV only after dark) that matches the black frame around the TV screen. So after a bad attempt with MDF trim, I went to 1/4" plywood covered with a black denim-print cloth. A 4x2 piece of plywood from Lowes, and 1 yard of material from Hancock fabrics gave me plenty of extra stock for re-do's if necessary. As the speakers are on the bottom of the TV, I drilled large holes in the bottom trim board before attaching the cloth. I used "Goop" adhesive (awesome stuff!) and a regular household stapler to attach the cloth to the plywood, and to attach velcro to the plywood to hold it in place above and below the TV ...using angle brackets inside the cabinet for the other side of the velcro. I did have to get the "wort" audio cable from River Park Audio in Elkhart IN to make the original Winnebago surround sound work. I am pleased with the result, and am amazed that after setting up the TV for local digital channels we do not have to get up and change the switcbox to antenna to watch locals ...we just move the channel selector from "4" for Dish and it goes right to the local digital channels!
You can see pics and some description of the process I went through on my website.
Edit: link in sig line.