Newmar put together a website called Newgle (
register here) that has a bunch of information about their coaches. They require your coach serial number to give you a login. The site is marginally useful. It does not contain wiring diagrams or the like for the house portion. No plumbing diagrams. But it does have links to manuals for all the stuff in the house as well as the chassis information from Ford. You would think that with your serial number they would only show what is in your coach, but they show pretty much anything they have ever used so you need to dig a lot. Maybe they will improve it in the future.
Gas gauge issue, that's Ford. Changing a sending unit is not fun, so hopefully it's just a wiring issue. Replacing the roof is a lot of work but is pretty straightforward. You will need to remove the A/c, skylight, all the vents and the metal trim that holds the edges with probably at least a hundred screws.