If it has a 6.6 duramax diesel. The fuel filter is on the passenger side under the wheel well. Remove the wires for the water presence sensor. Then remove fuel filter much like an oil filter. The water sensor needs to be reused and both o rings need to be replaced. Once filter is back on the system needs to be pumped up. There is a plunger on the filter housing. It needs to be pumped alot of time. While pumping make sure there are no leaks.