It's between the axle and the fuel tank. You'll need a ford fuel line disconnect tool that fits over the line and slides into the spring fitting to release it. It's really easy, but if your not real careful it's pretty messy. Open your gas cap to help relieve pressure, you can also relieve some pressure on the schrader valve on your fuel rail, just make sure to put a rag over it before you press on the little pin in the fitting. But the schrader valve thing isn't really necessary, because i have a fuel pressure gauge in mine so I can't relieve the pressure, and it makes no difference when I change mine.
In your trunk, left side behind the lining or whatever it's called, there's a small hole. You should be able to unplug the wire there that will relieve the pressure. Once it's unplugged, they recommend trying to start the engine. It won't start, and that's good. Then use that tool. Have lots of paper towels handy. You WILL spill fuel. Have fun!