If i were you i would do some digging on the internet about the project. I would caulk and seal the entire area you are putting the generator in, must keep the fumes out of the rv. Caulk & caulk again. You can go to an air conditions supply or similar place and buy a can of smoke, spray it in the generator area and have somebody in the rv to look for the smoke. I would then insulate the walls to help sound proof it. As far as the gasoline, i'm sure you can work that out. I would use a portable can so you could take it out to refill it. You can use a rubber hose from the gen. Tank, run it to the portable can, and it will siphon gas from the portable can to the gen. Tank. Use quick connect fuel line fittings from west marine or similar and they do a good job. Drill the top of the fuel cap to fit the fittings, more on that later if you need more info let me know. You will also have to vent the portable can so it can get air to siphon.