How can I remove the rear headrest to get the third brake light out?

There should be a couple of screws to the 3rd brake light up under the deck that are accessible from the trunk.

I found this online in the mbworld.org forums. So someone else wrote theses instructions. I used them to remove my old tint from my back window and hunt down a rattle from my rear subwoofer. Read more: http://mbworld.org/forums/cls-coupe-c219/440821-how-remove-rear-subwoofer.html#ixzz3EWcl0nNn You have to remove the seats. The headrests (a bear to remove) the c pillar moldings and the rear deck. Its a 8 hour job in the book but I did it in 4. You do not have to take the console out. The seat bottoms have buttons underneath and pull right up. Just feel around the front bottoms for the them. The seat backs have3 or 4 bolts on bottom. you will see 2 once the seat bottoms are off and the other 1 or 2 (cant remember how many) is on bottom seat back between seat and rear of center console. The seat back lifts straight up once the bottom bolts are removed. I did this to remove the old window tint glue and have the rear window re tinted. C pillars next. Then the headrests. The C pillars are secured with push clips then slide up and out of the notches in the rear deck cover. The headrests have little plastic levers that have to be pushed either up or down. The levers are located on the mechanism that swings to allow the headrest to raise and lower. You should be able to see one of them on the right side of the right seat headrest to get an idea of how it comes apart. I think the levers were black. When the levers are release you have to pull up while moving the little lever in the release position. I had to use a "L" shaped pick and a lot of patience to work the lever while pulling on the headrest. You cant really see what your doing so you have to kinda feel your way around. This was the part that took the most amount of time.