Question: Gas gauge not working,if it is sending unit how hard is it to replace. It is a 2004 liberty. Answer: I would check your fuses first. You will find specific locations in your owners manual under"fuses". If all your fuses are OK, then most likely it is the sending unit. The Sending unit is located inside the gas tank mounted to the side of the fuel pump. You will need to be in a well ventilated area. Too much air is a good thing. You will need to support the vehicle securely on jack stands. Find the Fuel inlet hose(this is where you fill your gas tank) and remove the hose clamp. Also, remove the hose clamp from the return line. Disconnect any emissions hoses that might be in the area. Using a jack, support the gas tank and then remove the gas tank mounting straps. Lower it down slowly and just down far enough to be able to access the fuel lines. Disconnect the fuel lines and electrical plug in. Lower the tank the rest of the way. Remove the lock ring by turning it in the counter clockwise direction. Lift fuel pump/sending unit from tank. Replace and install in reverse order. If you do not have the right jacks , supports and tools this can be considered a difficult procedure not to mention the safety factor of exposed fuel. I would recommend having a shop do this repair for you if you are not a certified mechanic, due to the potential dangers.