Almost certain they will be behind the passenger dash, well thats where they are on Sierras at least.

The relay should be yellow and is just a standard SPST relay, so you don't need anything special!

You can always bridge terminals 30 and 87 to test the relay and the pump, if the pump runs this shows it to be ok so either the relay or the ECU output is at fault, I still should think it's most likely bitten wires, or the relay could possibly be jammed in which case a "Flick" on the casing itself usually frees it.

Martin