$600 water pump job?
$600 sounds rather steep for a water pump replacement but you didn't id your model. Perhaps for a 500SL, I dunno, but my 1989 300TE should have been alot less than that. I did the water pump, serp belt tensioner, tensioner shock, and air pump for about $600 but that was doing the work myself and getting good deals on the web. Still, shop around if you can and see if your MB tech is out of line.