I've just done this job. Cam is not removed. It is recommended to only remove one rocker tower at a time so as not to stress the cam. Make sure you plug the drain holes in the head, you don't want to lose anything into there. Make sure you keep the rocker buttons?? matched to the lifters/rockers, you don't want to get them mixed up. The standard spring compressor with the thumbwheel worked fine for me. Use tweezers or dental picks to remove the keepers. Lock the crank with a ratchet against the pulleys to make sure it doesn't spin when you apply air pressure. Use an appropriate torque wrench for the tower bolts ie. not a 100lbs unit. You don't want to strip them.

Two thumbs up for the Mercedes hood design!

Jorg