I had to haul the car to the Benz Store and since they had it they went ahead and replaced it for me.
Yes, it is a simple thing, and I almost went ahead and bought one before I knew what the problem was. I had already replaced coils, plugs, connector, wires and fuel filter, but, several people said "Don't just throw parts at it" and I didn't have the diagnostic equip to find the problem.
The part was $279, with diagnostic time and R/R it came to $373.
I have spent much more, for much less!
"The grass is not 'greener on the other side of the fence'. The grass is greener where it is watered.
When crossing fences, carry water.