If it is the ujoint the driveline part number is 5135420AA and it is lots cheaper, I have sent you a PM on the price. By the way the Mercedes part number is A 170 410 28 06 , just FYI.
If it is a rear axle the part number is 5159990AA and the MB # is A170 410 28 06.

You could take it to a driveline shop and they could probably repair it cheaper like Stogey said. Make sure you tell them it is a SRT, there are three drivelines one for the auto trans N/A - one for the manual N/A and one for the SRT.