I think you should have the shop remove the pads and apply MB brake paste to the pads before replacing any other parts. Some slight brake squeak is not abnormal due to the high metal content of replacement pads. Also if they did not install genuine MB pads you may want to have them do that if the paste does not correct the problem. The part number on the MB paste is 001 989 47 51. Hope this helps, Robert.
Mercedes Benz Master Tech