I'm seconding the mind of it'* own that WillWren mentions on 2 sensors from Advance and 1 from Napa. Soon..I'll be getting a new sensor..
To locate the sensor..
Jack and support the front of the car.
Remove passenger side tire.
Remove splash shield to gain access to the lower back of the motor (behind power steering pump, caevat..not sure if the 00'* have a splash shield in this location)
The oil pressure sender will be a black/gray tubular sensor behind the power steering pump to the rear of the motor.
As it is not a normal socket size.. I suggest either buying the specialized socket or carefully using channel locks on the metal part of the sensor only.
00 Regal GS: All kinds of cool stuff.