you need to undo the four screws located at the top of the rear window, you then remove the whole spoiler, to access the screws that hold the light in place. as Bob says you need to replace the whole light as its made up of LED's. I ordered one and was told it could be three weeks, check the leds have gone before ordering a new one as they cost over £50 new. and when we checked mine it was not faulty, it could be a wiring problem. so check to see if you have power to the light first before getting a new one.
Greg, October 2010