I have installed two TV's in a 40' diesel motorhome and other devices in several other motorhomes so I can offer some suggestions.
The primary problem with mounting anything in a mobile device is locating a frame member strong enough to hold the device. Trailers and some motorhomes are weight limited by the under carriage so the super structure is a careful balance between weight and strength. As such, it is imperative that you locate the actual structural member behind the facade of the interior.
Another problem you will face is the electrical wiring and other services are frequently contained within hollow structural members as that will hold them in place during manufacturing. You must avoid these to to avoid even more costly repairs.
The dealer has likely already seen where these items are located and can immediately drill the proper holes and make the attachment with minimal trouble and if the dealer drills a hole in your power wire then he will be responsible for the repair.
With that said, I continued with the job myself. The hard part is locating the supporting struts behind the wall. It sounds like you may have an identified location where the TV is designed to go. If that is true, then the tape could identify the proper spot. One way to test is to use a small rubber hammer and tap the wall. If there is a solid wood support behind the tape it will sound different from the surrounding area.
Once an area has been identified, I used a special drill to drill test hole. I chose a 1/8 inch drill. With the drill in the drill chuck, I cut a piece of 1/2 inch wood dowel such that when I drilled through the dowel length wise, only 1/2 inch of the drill remained exposed. Thus you have a drill that will only drill hole 1/2 inch deep. I chose 1/2 inch because most inside walls are 1/4 inch plywood so the drill should reach only 1/4 inch into the backing material. This should be enough to identify the material. If you hit wood or aluminum you are in luck. Continue to try each hole location. If you hit Styrofoam you need to move elsewhere.
One more tactic is to use a sheet of 3/8 plywood l the size of the mount and connect the mount to the metal. Then you can use a dozen or so small screws and glue to hold the plate to the plywood wall. For small TV's that could work as well without the need to find a mounting.
Good luck with your endeavor.