Thejack - I don't know about the C-Class specifically, but I do know that a VW Passat for example can accept European Bi-Xenons that will plug and play into the wiring harnesses - BUT they do not have the necessary sensors to enable automatic levelling. There is significant wiring and sensor placement to enable auto levelling, and most people do not do it. It is a tough job.
It may be that its the same for your C-Class. There may be a manual levelling motor and switch that is easier to install, but will not adjust automatically while driving.