I guess we assume this to be a US version MB. They all DO have OBDII connectors since 1996. Of course an OBDII connection is useless for anything other than OBDII which is rather useless on a MB anyway.
I'm not sure ROW cars have OBDII connectors.
If you really wish to deal with this issue on the 38 pin connector I would suggest spending $18 on a one day subscription at
www.startekinfo.com The complete designation of the 38pin connector and the OBDII connector and their relavence to your car will be there along with the complete diagnostic manual for every system you could question at either connector. Many of the documents on the site are pdfs that are downloadable and thus useable forever.