I have not seen a Bentley Manual that has the 300D 617 Diesels.
If you are going to get a Haynes or similar Manual get a used one on eBay or look in your Public Library. The info in the is somewhat minimal.
I dissagree that you don't need the Factory Service Manual. Depending on what you are doing the Forum is not always going to answer your question in a timley manner and then you are sometimes going the way someone else did something that is not going to work for you. Other times the Forum has ways to do things to get around the Factory Tools and so on.
My point is that the Manual is sort of a minimum starting point.
You are supposed to be able to get the CD or DVD Manuals from below:
Part numbers for service Manuals STARTEK
Star Service CDs and DVDs
Contact Consumer Promotions at 1-800-FOR-MERCedes for current pricing and ordering information on the accompanying CDs and DVDs that are available for purchase.
People say the Manuals are free for viewing on Startek. But, I believe you need to register with them.
The Mercedes Manuals on CD do not cover any Transmission or Turbo Charger rebuilding but otherwise cover the whole Car.