not easy to get one in the uk and not cheap if you could but help is at hand
http://www.benzworld.org/publications/pub.asp?id=244
http://www.benzworld.org/publications/pub.asp?id=245
even though the 190e isnt on the data list "yet" the proceedure for extracing the codes is the same for all the mbs look at page 277 on the first link it shows hot to get started