How much does it cost to replace the fuel gauge in a 2000 JAGUAR VANDENPLAS?

Hello, it sounds to me that it could indeed be the gauge, but it could also be the wiring. The gauge is only responding to voltage in the wiring, which varies depending on sending unit position. Proper test equipment can active command and monitor the gauge and sending unit positions independently so that you can isolate the problem to gauge, wiring or sending unit.