A cracked cast iron head is kinda rare. More likely it's a head gasket problem again. MB changed their head gaskets several times. The new ones are NOT to be exposed to air until they are ready for immediate use. Be sure to let it rest and follow the directions shipped with the new gasket.
You could certainly have other problems but if it didn't freeze or overheat, it's probably a head gasket.
FWIW: MB wants you buy new style (use them once) stretch bolts. I like the early hex drive type and they work just fine. Simply torque them down in proper sequence to their original specs. I do re-torque them at the 1,000 mile oil change and final valve adjustment.
Or you could get the newer stretch bolts.
DON'T get your block or head surfaced unless you have one helleva gap under the straight edge. A light pass with a DA to remove gasket crap is all that is usually necessary for iron. The hatching gives a good grip for those new, more pliable, head gaskets too. If you have them surface cut, you will find out why Mercedes sells those offset camshaft sprocket keys
