I remember MBenzNL (Steve) mentioning somewhere that the motor is available as a spare part for some other MB model but I have no notes about that part number.
Anyway the light unit is glued and difficult to open. Some say they've put it into a kitchen oven for 10 minutes and the glue gives up nicely, also works backwards (you have to be careful though, your wife might interrupt you in the middle of the process
There is also a batch of light units that fail because of the internal wiring getting exposed, in this case the motor could be fine.