It is under the dash, towads the center. Its mounted in a "conveinience center" (has all of your flasher relays and such).
You may need to pull some of the lower trim off to gain access to it.
I don't think the relay is going to fix your problem, because the oil pressure switch isn't to shut off the pump in case of oil loss, its supposed to allow the pump to run in case the relay goes bad, providing you have oil pressure. The oil pressure switch is a "back up" should the relay go bad.
OK, look at this wiring diagram for your fuel pump:
If you look at the output for your relay, you will notice it has two wires, one to the pump and one splices into the wire from the oil pressure switch. So either component can operate the pump, both are not needed. If the switch fails, the relay will work the pump and if the relay fails, the switch will work the pump.
So if you put a new oil pressure switch in there, and the pump isn't getting voltage, then you have another issue, probably not the relay.
As far as whats next to the relay, I don't know off hand, but if you swapped it and it still didn't work, that further confirms that its probably not the relay. You either have a wiring issue somewhere or the fuel pump is bad. It is possible to have an intermittant fuel pump.