I have not had any work done by this person but I did visit his shop.
It is a small garage in south Philadelphia.  I believe he works alone.
He may be retired by now.  

Nazzens  MB   215 551 2222

Another one is German Auto Specialists ( they do Porsche, MB, Audi
etc...) I discussed my tensioner problem with them to get more views.
610 279 8500  They may be more expensive but appear well informed.

On the subject of the tensioner,  I may have solved the problem in my
shop ( my own maintenance).  All pulleys must be checked with a dial
indicator for trueness and in my view should not be more than .1mm out
of round. (1/10 mm) .   Alternator shaft and pulley, water pump with
pulley, a/c pulley and  power steering shaft and pulley.  To do this
you need a good dial indicator with a range of  .2 mm.  Starrett makes
one.  If the shop does not have one they can not identify the problem.

Hey there -

The mechanic that I use and have used for about ten years is George Law
and Son in Wayne Pennsylvania. He is a mercedes specialist, and has
worked on a variety of older diesels including the one that he owns and
drives. He has done great work on my father's 1991 SDL, which has 178K
miles on an unrebuilt engine. I can reccomend him.