Too late now, but it looks like I forgot mention that there is also a mark on the first cam bearing cap which should coincide with a mark on the cam or cam gear (I forget). Having it set so the rotor is pointing to the #1 terminal achieves the same thing but the lining up the marks makes it precise.

Sounds like it worked out though. If there was oil in the cooling system, flush it out well. Mercedes has a few specific flushes in powder form one specifically targets oil and the other I think is for like scale, rust, debris, etc. If you don't have a bleeder bolt on top of your thermostat housing, bleed the remaining air out of the cooling system with one of the two large headed bolts at the front of the head just under the oil filler cap.