On my 1990 FWD I did not need to remove or lower the tank. Yes, the plate at the back with the screws around it is the access panel. Yes the bolt at the bottom of the tank holds in the pump. On mine, removal of this bolt only caused gas to drip. Actual removal of the pump assembly takes rotation of it to fit it out the hole.

The cover bolts on mine were an absolute PITA...good luck