GMC Repair: 2002 GMC Yukon XL - Illumination bulb out for Rear Window Def. Button, gmc yukon xl, gmc yukon

Question
I have a 2002 GMC Yukon XL.  The rear window defogger button (also controls heated outside mirror) seems to have the bulb out that provides illumination from the rear.  The button works fine - it just isn't lighted so I can't see it at night.   How do I replace this bulb?

Answer
if it is possible to replace the bulb, you can find out what kind at sylvania.com, you enter your vehicle info and it will list all the bulbs that are replaceable on the vehicle.  On some vehicles you have to replace the entire control head, I am not sure if this is one of them