This is the official site but I don't see a W210?
Star Service CDs and DVDs
I bought My W123 CD Manual back in 2007 from this place and paid double what it would have cost if I had bought it from the Mercedes Classic Center.
Since, that time I have twice tried the CD Manuals from eBay and neither of them worked. Mercedesmanual is a reputable company.
I did not look to see if they had the one you need as I don't know what year your E300D is.
http://www.mercedesmanuals.com/
Bently may have a Manual but for the W123 there is no Diesel Engine information; Bently may do the same with the newer ones; no Mercedes Diesels. Although the Bently VW Rabbit manual has the Diesel Engine information.