Engine replacement

I have a 2002 330ci convertible, which is my pride and joy. It is in perfect shape, body wise. Unfortunately, my head gasket blew and both the local BMW dealership here in Utah and a local recommended mechanic wants $4600 to fix with no guarantees. They said there is a possibility that if the head is warped to much that I may need a new (used) engine. Looking ahead, my question to all of you is if my head is warped and I have to make the decision to replace the whole engine, what is a...

Engine replacement