Try contacting Xplorer if you haven稚 already.
Hopefully they値l help.
Re: the fuel tank / fuel line
From memory, (on my Roadtrek) it looked to me like they just tapped in a hose barb type fitting into the tank. There was a rubber hose attached to it. I値l look at my current RV setup this weekend.
Forum member g1g has done quite a bit of work related to his generator he might have more specific advice for you.