406 saloon fuel sender

After a struggle have managed to remove rear seat, the Haynes manual says that the fuel pump can be accessed by removing a circular plastic plate, however I find that this is covered by a triangular plate rivetted into position, is it alright to drill these out? I find that the wiring on this car is generally shaky with all kinds of odd things happening and despite being a retired electrician am nervous about touching anything, would imagine that the connecters they use are prone to corrosion.