When I asked Newmar to add it behind the PS couch on our 2008 they said it would be about $3K. Sounds like a lot but when you add the cost of a new TV, the mechanism, the woodwork, and the rewiring of electric and cable, it's not too bad. But, we still didn't do it, maybe next coach.
w/Lucy the Dog & Jack the Cat
2008 Newmar Mountain Aire 4529