I have had a problem with gas leaking when I fill the tank. The repair shop did a quick check (did not drop the tank) and they think that its a gasket on top? Anyone know if this sounds right? The leak is on top and not aroint the filler hose. What is on top of the tank that has a gasket?

The fuel pump unit and sender unit is up there. There is a lock ring and a gasket.

Thanks for the info!