I have fixed similar problems without dropping the tank by pulling back trunk carpet (or other depending location), carefully drilling a 2" - 3" hole using a hole saw, thus accessing the area for repairs. Fasten a sheet metal plate with gasket over it when done and put carpet back in place. To prevent the drill from drilling to far (falling through and damaging below) I use a couple wood blocks under my drill that the drill hits before it drills to far.