Replace the bushings in the ends of the shift lever linkages connecting the column shift to the transmission (under the car). Also replace the bushing in the pivot ball of the lever itself (unscrew the chromed hex nut). These are made of a plastic material and fall apart with age. Easy jobs for the DIY'er. Available through the Mercedes dealer, or try the Buy Parts tab above. This should take care of most if not all of the slop.