Rodent damage to fuel tank fitting for generator supply

I have a 2011 Jayco Greyhawk that started having a problem starting the Onan 4000 generator. Suspecting that I had a fuel pump issue, as no fuel was getting to the pump, I changed the pump and filter. No joy, that did not help. I now started to check the hose for any signs of damage, found nothing til I got to the fitting on top of the tank. The fitting looked like it had been chewed on since the corner of the 90degree fitting was missing. It is obvious that it needs to be replaced which will require dropping the tank. I have no problem with doing that but the one area that looks to be very tough issue is disconnecting the fill and vent lines. There is no obvious access to get to that area of the tank.
The tank is a 55 gallon standard Ford tank.