Just for clarity, it's not actually under the rear seat. It's under the car. Passenger side inboard just in front of the wheel well. Look for black plastic cover. I think the fasteners are 8mm, maybe 10mm, and as previously stated, you will need a 6 inch 1/4 drive extension for the deep one.

The rest is self-explanatory. You will get some fuel on the ground and on your arms. One thing you can do is take some needle nosed vice grips with a red shop rag to cushion the jaws and clamp of the rubber hose from the fuel tank to the fuel filter. Do this before you loosen the nuts. Be sure you look at the direction arrow on the old one and install the new one in the same direction.

When you are done , start the car and look for leaks. Then replace the cover.

Steve