You do not have to remove the sunroof panel but you do need to remove the sunroof headliner to get access to components. The cable runs in a tube from the front of the sunroof panel to the motor-gearbox in the left side of the trunk.

The most common source of a slow-running sunroof is old, dried grease in the tube and on the cable. If your roof runs better when it is warmed by sunlight or in warmer temperatures, you can be sure that is the problem. I have dealt with this and the repair went well.

The procedure is long but not difficult. I recommend the "kit" offered by mercedessourxx.com. It contains instructions, the correct greases and a bore brosh and wire arrangement for cleaning the inside of the tube.

This is not a difficult job and very satisfying when finished.