Fuel Filter. where is it and how do I replace it?

It's in the fuel tank and is part of the fuel pump. You don't replace it unless there is a more serious problem. (i.e. fuel pump)

The Fuel Filter for your Truck should be on the Frame under the Driver's side of the Truck, between the tank and the engine bay. All you need to remove it are a couple wrenches and a catch tray for the fuel that will leak out.

There is a filter in the tank as well but I believe the one your looking for is this one...

Make sure you de-pressurize the fuel system before you take out the old one. It's a pretty simple job and I believe shops charge about a half an hour labour to do it and the filter itself should be about $20-30.