The first thing I would do is drain the oil and check the magnetic drain plugs for metal shavings , if they are present then you know a bearing is bad . The procedure to replace the bearings was to remove the differential center section from the car . With the diff on a sturdy work bench remove the rear cover inside you will find large c clips that hold in the stub axles , before you remove them place a locking tool or a rag in the gear and remove the nut for the pinion flange then remove the c clips . You will need to get the center section out of the housing they are a tight fit ( I used 2 large prybars factory tool is a spreader setup ) . Take very close inspection to the side to side adjustments of the carrier bearing adjustment shims and do not change them .I also used some gear marking compound it is painted onto a section of the ring gear and you spin it thru the pinion gear and you can see the pattern of the gears meshing . Once the center section is out you can check the condition of the carrier bearings mine were ok . Remove the pinion from the housing and press off the bearing from the pinion ( you may need to tap the pinion out of the front bearing not a problem if being replaced . Tap out the bearing races from the housing and replace with new ones . Press on the new rear pinion bearing replace crush sleeve and reinstall shims . Install into the housing and install front bearing and pinion flange . When torquing pinion nut do it in several increments and spin the pinion to be sure it does not lock up . When done the pinion will turn stiffer than when it was taken out from the new bearings not being worn this is normal . then I rechecked the pattern on the gears to see if it was still the same . I hope this helps you to make a choice as to do the job yourself I would have a repair manual for reference . I have done differential repairs before just not on Mercedes . I cannot afford to have a shop work on my cars so I do everything myself that I can . I also work on Italian cars for a living ( no Fiats ) .