First, pull the gray pin switch on the trunk lid outwards just until you feel it click in to place. This switches off the trunk light which helps when removing the light housing as you can short it out and blow a fuse during the removal process (When you close the trunk lid it resets the switch automatically). Next, take a small flat screwdriver and insert it into the small indent on the right or left side of the the cover and gently push inwards and twist lightly as not to scratch the paint and it should pop out. Replace the bulb and push the housing back into place and voila!. You'll know if you shorted out the circuit as the backseat light is on the same fuse.
I had originally tried to pop out the housing by pushing on the left side of the housing with a flat head screwdriver except I did not twist it a little as you suggested. The result was that the housing seemed to be loose but would not pop out (I tried this several times). Maybe that little bit of a twist is what I need to get it to pop out. I'll try what you suggested (by the way, thanks for letting me know about the grey switch on the trunk lid bottom) and hopefully I don't break anything.
They can be a bit stubborn, but they do come out. Twisting the screwdriver helps control how much pressure you put on it so that you have less chance of breaking a tab then when pulling on it.
The trunk switch is handy if you know you are going to have it open for a while you don't need to be continuously leaving the light on. Germans put a lot of neat little usable features on their vehicles which the Big Three should pay attention to. Then again, you get what you pay for...
BenzWorld.org forum is one of the largest Mercedes-Benz owner websites offering the most comprehensive collection of Mercedes-Benz information anywhere in the world. The site includes MB Forums, News, Galleries, Publications, Classifieds, Events and much more!