RE: 2005 C230K Left Bumper Side Marker Light Bulb?
Page 350 of the owner's manual:
1. Carefully slide the lamp towards the REAR of the car.
2. Remove the front end first.
3. Turn the bulb socket with the bulb counterclockwise and remove it.
4. Insert the new bulb into the bulb socket.
5. Place the bulb socket back in to the lamp and turn it clockwise.
6. To reinstall the lens, set the REAR end in the bumper and let the front end engage.
PS> it takes a little nudging to slide the lamp towards the rear, but it will go. You need to do this because there
is a small plastic piece on the FRONT that you will break if you just pry the lens out without sliding it back first.