If its the same thing as the oil pressure sensor, I changed one of these without knowing anything about cars, having only ever changed a wheel before. My warning light was intermittently on, and was quoted $300+ from a range of places to sort it out.
For my 5.7L SS I got a 27mm socket from supercheap, you need something with a long shaft as it has to reach through a tight gap. Its down near the back of the engine on the passengers side, pretty hard to see if you're not sure what you're looking for. Unplug the clip in cables, then it's a game of operation to get it off and on. Got quoted $190 for the part from holden, $220 from supercheap, but got a $39 brand new legit GM (supposedly) one from a place in melb I found on ebay (picked it up in person to make sure). 7 months on no problems.