Unfortunately, I had a poor experience when asking ny dealer for the initial oil change at 1500 kms. They growled and moaned about not needing to do that change, despite the fact that I was supplying the oil and paying for the service. Reluctantly they took it in and told ne all done. When doing service two, myself, I discovered they actually had not even undone the engine sump bung at all.
Sadly, the dumb AMG design of having no physical dip stick means there is no way of seeing the colour of the oil, old or new.
Needless to say, that (or any other dealership) do not get my custom.
With the foregoing in mind, perhaps you either could watch the change take place, or ask for the second service to be provided complimentary. You could always get the first service done at another service centre, one who will actually undo the engine bung and drain out/refresh the oil.