Benzboy, I'm in the same boat as you! I have an armload of suspension parts and I've been calling around for quotes to install them. The basic difference is that the dealer charges $18/hr more than the best local indie shop.
Based on the quality of past service at the dealer, the special MB equipment they have and the exclusive MB knowledge they have, I'm going to go with the dealer.
BTW, our local MB dealer sales, parts and service are separate departments and the service manager told me he doesn't really care where I get my parts from....but the parts manager might
It was interesting sourcing out the parts on internet....saved about 30%. Some real crap for W124's on eBay, Chinese and Italian stuff
I've gone with Lemfoerder all the way.