in germany we are able to buy "WIS - Werkstatt Informations System", this is a
database with all classes of mercedes and it's used by the mercedes technicans
also. you will probably find some versions on ebay or somewhere in the www.

there is a second cd called "EPC - Electronic Parts Catalogue". that is the soft
they need if you want to buy a spare part. this one is not so interested if you
just need a "how to".