Joe, Indeed it is called an Overload Relay on Fastlane. You found the right one (about $49.00). I went to other Mercedes sites and it was called an Overload Protection Relay and Overvoltage Protection Relay. Take your pick. At Fastlane though it is the Overload Relay that you want. By the way, Fastlane had better prices than the other two sites.
There was a thread sometime back on this site that showed a photo of the OVP and Fuel Pump Relay and their location, but I couldn't locate the thread again.