Egads, man, get that thing offa there!
The dealer will do it all free, and they are paid to inspect the turbo as well. If there is any turbo damage, they give you a new turbo as well - free. If the turbo is OK, they do NOT replace it. Some dealers try to weasel out of this job, or claim you're not entitled to it, or whatever. If so, print out the following three documents, and go beat them over the head with it - plainly states the details of the recall:
http://www.meimann.com/docs/mercedes/trap_oxidizer1.pdf
http://www.meimann.com/docs/mercedes/trap_oxidizer2.pdf
http://www.meimann.com/docs/mercedes/trap_oxidizer3.pdf
HTH,