Be prepared to Replace the head due to a crack. I bought a e34 with a " blown head gasket" turned out to be a cracked head. The twin cam heads crack.
On the M50 engines my experience has be a 50 - 50. RE head gasket vs cracked head.

I have seen a few M44 318 cars for sale with cracked heads. So it happens on this engine also.

You may want to try floridagerman.com there are a few shops in the BMW area. They will be able to give you an idea of a price. Replacing the head is a pain.

Intake, Spark plug wires, Exhaust and cooling hoses all need to be unhooked. There is a plastic coolant hose on the back of the head that is a pain to get to. On the 4 cyl there are 2 plastic coolant hoses that I would replace if you have the head off. about $25 in parts. I have seen the one off the back of the head cause 2 engine failures.

Hope this helped.

B