I have lost the car manual and the garage is telling me that the bulb-like lamp that is showing up on my car indicates that a service is due. I suspect they put diesel in my unleaded engine and that is the real reason why my car is giving trouble. Would the service management lamp on a Mercedes not show up as a spanner icon?

 

There should be a display on the dash that shows a little picture of a light bulb and what is due.
If you suspect "they", meaning the garage, put diesel in your car, I would not return there. I'm not
sure how you know that they might have done this, but......I would not go back there and confront them
about it, because of course, they are going to say they didn't no matter what. Of course. I am guessing
that is not your problem, but it's hard to say sitting here behind this computer. A competent shop can do
the service necessary and siphon out the "diesel" if you think that's what is in there and fill your car up with
unleaded gas. I suppose anything is possible but that's a good one! Please let us know when you find out
if that, in fact, was what they did.