My 95 E300 is my favorite MBZ I've ever owned, including much newer V8/AMG-powered cars like the one I also currently have. The OM606 is an excellent motor, mine returns an easy mid-30's MPGs and has plenty of highway power (they can be a bit doggish at low RPM). Typically they have head jobs for a few reasons:

1. it was overheated badly, in which case any motor is doomed
2. neglect and the incorrect coolant was used for a LOOOONG time (use only G05 Zerex)
3. this seems to be the most common, someone broke a glow plug off in the head. This is very easy to do and Lubro Moly anti-seize should always be used when doing the glow plugs, which in turn should be done without fail every 40-50k with Bosch.

Usually the non-turbo OM606 head gaskets are stout, I can't speak for the turbo as I have never owned one, but it's a great engine and if you get the head work done it should be good for another 200k easily with good care.