At present, you have 3 options...
- There are model year introduction to service manuals out there. These are MB factory publications. You'll have to cobble together just the right ones and they'll leave lots of holes.
- There are dealer only manuals. Finding those are tough. I acquired a set of 7 loose-leaf bound diagnostics manuals that cover the 129 & 140 chassis cars. These came from an estate.
- There is an "Information Access" classroom training CD. FOr a glimpse at a similar disk, see http://cgi.ebay.com/ebaymotors/aw-cgi/eBayISAPI.dll?ViewItem&item=570510653
This is another dealer only item. Also, it's NOT a service manual. It won't help you change your oil. It WILL give you a complete subsystem by subsystem introduction to the car and how those systems work.
EBAY is the only source for this stuff or literature brokers like Schiff Automotive and TCM publications.