We had the floor in our coach re-carpeted a couple of years ago. I agree with the post above that an independent carpet installer is the way to go. Find a good carpet store near you - not a box store or a chain. They should have a Roledex of sorts filled with names of local independent installers. If you explain the application, they should be able to recommend someone who has experience with motor homes and travel trailers. You don't want someone learning on the job with your coach.
We used a nylon plush carpet which was fairly dense. The more yarns, the more it will hold up to heavy traffic in the main walkways of the coach. Polyester has come a long way, but it was explained to me that nylon is still better and about as good as you can get without going with wool.
The installation on ours was different than I expected. The installer recommended a dense rubber type padding, which he glued directly to the sub floor. The carpet is then glued to the padding. The only places which were stapled were a few parts of the stairs and as he wrapped around the bullnose where the floor met the stairs.
1974 GMC 4108 - Custom Coach Conversion