Pay attention to what WARDEN says. He is a frequent contributor to thedieselstop.com. In fact when I was looking for MB diesel, I posted on that board and he told me anout mercedesshop.com. His summary hits all the high points.
My '86 F250 6.9 auto has just passed 325,000 miles and I rebuilt the engine--After completeing the rebuild, by assessment is that it really only needed a valve job as the original hone marks were still visible in the cylinders--not real deep, but visible. I love my truck. Oh, and even with the non turbo 6.9 auto it is still faster than my 240D. In fact when I'm pulling my 6000lb 5th wheel I think its about as "fast" as the 240D.