The fuel pump on a 94 Chevy Impala SS is changed by lowering the fuel tank, disconnecting the wires, removing the fuel lines, and unbolting the pump. It can then be lifted from the tank and a new pump put into place.
To change the fuel pump in a 2005 Impala one will need a fuel pump kit, socket wrench set, and a torque wrench. The gas will need to be drained from the tank and the battery will need to be disabled from the engine. The fuel pump is located inside of the fuel tank.
It is located in the fuel tank but you can get to it through your trunk. Just take off the carpet in the trunk and there is going to be a plate with eight screws i believe. Take that off and you will be able to access the fuel pump.