Resistor is located in a very un-ideal location.
Remove your front passenger wheel.
Pull back your liner inside the fender to reveal your washer bottle.
Remove the washer bottle, and you will see the resistor.
It's about the size of an I-pod, made of ceramic, and only available through GM.
Fuel Pump Resistor Kit (Includes: Resistor Zip Tires Wiring Harness) 88951182