It's the same as C220/C280/C36/C43/E320... etc... depends on year of car what alternator you need. I know up until 1996 W202 and W124 used same part. W210 did as-well. Looking at your car you have a 1997 or newer so I would check with the dealer but I know for sure is shouldn't cost too much money. I can get a used one here in the states for about $50.00. Of course it would cost alot more from the dealer.
the bosch site states that the law has changed with regard to having your car serviced at main delaers to ensure the warranty is valid. Would have thought this was dependant on the warranty terms more than anything else.