Jimm 7/7/2012It should be on the black tin plate on the front panel. If not it should be inprinted on the bulk head (firewall). I think on the driverside if not then the passenger side. It might be covered by the sound deadening but there should be a little cut out.
Try the many on-line auto parts sources, such as; www.RockAuto.com or www.autopartswarehouse.com for the replacement parts. They (RockAuto) list the center link from around $21.00 for your vehicle. They carry center links from all the OEM suppliers for the Mercedes - same quality as found at the dealership except much less expense.