The problem with this job is removing the shells from the hub.
There is almost no lip to catch on to, Mercedes have a special puller, most of us shadetree mechanics would use a punch and a hammer.
The inner shell is quite easy, the lip is enough to get hold of, but be careful about the outer shell.
If you do change them, don't overpack them with grease, and then tighten them up until you feel resistance to rotation, then back off enough to allow the thrust washer to just turn under finger pressure, ie. quite tight.
Check them after a week or two, because they will need retensioning as they tend to bed in a little.
1989 W124 300E
1991 R129 500SL