On the ML mine needed the adjustment when the vehicle was new so it was done under warrenty. As I recall it did not take very long.

Just the other day I adjusted the shift interlock cable on my 124 wagon. The way it works on that vehicle is there are two cables that go to the shift lever. I don't know exactly how to describe what it looked like but there are two cams, when you turn the key one releases and when you step on brake pedal the other releases so you can shift out of park. I could shift my car out of park without stepping on brake and that was the cable I adjusted. I had my 124 wagon pretty much apart for evaporator replacement so it was very easy to access the cables. I suspect the ML is pretty much the same type of setup but I'm not sure.