That is strange that the pushbutton unit is faulty.
To remove it, you will have to take out the center lower wood first. You will take off the ashtray, ashtray wood, the find the hidden bolts inside the compartment opened by ahstray wood removal. Then the lower wood will come out. Next the radio and the other retaining screws will have to come out. Then the upper wood.
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS