If I understand this, you have supplied the parts and the dealer is doing the labor.
Guess who eats any additional labor if the head you've purchased is flawed?
I hope this all works out for you; it sounds to me like something is wrong at the dealership you've taken your car to. Is this an MB dealership? I'd call Mercedes if it is.
1991 300-SEL - Model 126
M103 - SOHC
James Madison - Oppressors can tyrannize only when they achieve a standing army, an enslaved press, and a disarmed populace.
Liberty Firearms Training - After years of trying to regulate California criminals with a never ending stream of gun control laws they have still not given up with the belief that if they make something a crime that criminals will miraculously start obeying the law.