Oil pump replacement

It's in the oil pan.
You will need a repair manual from the auto parts store for specific directions, because it is not a job for many at home mechanics. You will need an engine crane, or another way to lift the engine up without using the front pully (you will messup the harmonic balancer). If you have no way to lift this engine, you will not be able to get the oil pan off. You need enough clearance between the engine and oil pan to disconnect the pickup tube, before sliding the pan rearwards to remove it.
These oil pumps are very prone to losing their prime, so make sure and double sure that you are following the directions to the tee when replacing it! If not packed with the correct grease it will never be able to suck oil. If your pickup tube is positioned in the wrong spot during reassembly, you will run your engine dry, and cause terminal failure.