I think most modern cars have an ISO - connector. If your Mercedes doesn't have one just go to a shop which sells car-parts. Usually you should get a fitting adapter there.
I don't exactly know which connector the Mk2 has (will have). But I think the empeg docking cage is delivered with cables (rob or anyone who knows: am I right?) to connect to the car outlet. If so you could mount any connector you want to the cables to fit your car.

In my case I did the following:

My car has an ISO connector (one for the speakers and one for the power)
the empeg doesn't include an amplifier so you will have to install an extra amlifier.
I installed a 5-channel amplifier and connected the speaker-outlets of the amplifier with the ISO-connector for the speakers. So I just have to feed the amplifier with the pre-amp. So I mounted a pre-amp cable from the dash to the amplifier. I just have to plug in to the docking cage then the sound-output is ready connected, I think.

The next part is the poweroutlet. I don't know how the cables or the connector of the docking cage looks like. If it's an ISO or some other standard or even some nonstandard. I think in the description of the empeg how to connect to the car (hope there is some) there will be a description of the pins. So you just have to connect the pins correct to your car-outlet and then it'll work. (I hope so)