yes you can replace it,you dont say the make of car,but remove the carpet from the boot,(disconnect the car battery first ) you should see the top of the petrol tank and the round cover of the sender unit,(unless its a merc,then its under the rear seat)remove the wires from the sender unit,take note of where they go,remove the fixing screws,withdraw the unit complete with its float,go buy yourself a new one,c/w with a new gaskit
then reassemble
gts, May 2015