I had a similar problem in my Suburban. Dropping the fuel tank seemed easy enough. But to re-install it, it became evident that the filler hoses and the delivery lines have to be connected with the tank nearly in the installed position. This leaves very little room or line of sight to ensure these lines are installed correctly. My filler hose was not on all the way and worked itself loose and was discovered later at the gas station with fuel all underneath.
I suspect the same is true for most all vehicles with gas tanks that drop from the underside.
I had a similar fuel pump failure/tank gasket failue problem in a Peugeot 406 (Darn sight more comfotable ride than an RV!).
Recognizing the safety hazard, I had the car towed to a dealer, where the prodedure was first ro remove the fuel tank from the vehicle, then peform the work on the isolated tank in a safe area.
Fuel pumps are buried in the fuel tank because the liquid fuel cools the tiny overheating motor. If you are in the habit of running the tank dry, the motor will eventually overheat and burn out. I suspect the original design of your RV vehicle chassis didn't take into account all the extra electrics that would be piled on - RV's are usually adapted commercial vehicle chassis.
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