I have never done a 124 but have done lots of 123, 116,126, 115 rear bearings... Odds are they are the same..
You will need to drop the axles at the CV joints, Remove the rear brake calapers and disk.. Can't remember if you need to drop the backing plate.. remove the CV joint attachment from in inside.. for removing the stub axle the nut is inside with tabs bent so need to be sure you get those ... You will need a REAR AXLE SPLINE SOCKET. I got mine from
for 44 bucks but there are lots of other places to get them...
You will also need a slide hammer like used to pull brake drums on the old solid axle american cars as the bearings are slip fit and are tight... For the slide hammer I got an old steel wheel and cut the outter wheel off and made a slide hammer by welding a raised area that I welded the nut to for the slide hammer.. That way I am pulling with all 5 lug nuts.. I have several slidehammers but none that would work with the MB stub axle..
You will also need to have a way to hold the rear axle stub while you tighten it after as it has a crush sleeve to get the play in the bearings right...The holes to hold the wheel on are in the stub but odds are you will just bend wheel lugs if you try to use them with a bar to hold the stub axle.. I just have an old piece of 1/2 by 4 inch steel about 4 feet long that I drilled holes in and cut a place for the center of the axle to stick thru and use a couple lug nuts so its tight..I just let the end of the holding bar rest on the floor ...
The problem with using the slide hammer is that the bearings will have marks from taking them off so Mercedes does not use this any more if you are just checking and repacking..
All in all.. This job is not easy.. and unless you are planning on doing them often or keeping it for ever I would just take it to some place and have it done... But as you see.. I did not..