I used to have a '92 300 SD. In support of it I found 2 older Mercedes manuals. The first is an OM 602-603 diesel manual. This is pretty detailed and about 2+ inches thick. The second is for 1992 W140 - a high level service manual. It is about an inch thick.
The manuals are free to pick up ( N Phoenix, AZ 85086) or I can mail if you cover the postage.
PM me here or email to
chuck.schmidt@att.net if interested.