If the timing chain broke, you most likey have a bent valve...You will have to pull the head to replace the valve.
When you roll the engine to #1 TDC on compression stroke, there is a mark that lighns up on the distributor rotor to the distributor housing...You can't adjust it other than this. It is crank fired, computer controlled ignition timing. All you need to do is get the rotor in the right place to jump the spark over.
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS