You should deal with this problem. The pulley on my alternator came apart in two pieces a few months ago while I was driving. I think the cause was a bad belt tensioner which, most likely, caused vibrations on the pulley. Anyway, the tensioner was also bad and had to be replaced.

INA is a good brand. They make some Mercedes parts.

I guess you are talking about repairing the Y or V shaped part that holds the spring and small shock absorber. I have no idea as to whether it can be repaired. I think the better choice is to replace it.