1999 BMW M3 repair

The details of what happened are unclear, however, I will give an opinion. The M50 derivative motors (yours is an S52) have a tendency to have cooling system related failures that can and quite often do lead to cracked cylinder head castings. Here is the scenario, let me know if this is accurate. You were driving along, the engine was at normal operating temperature, you notice the temperature was high at the gauge, or perhaps there was a catastrophic coolant release from somewhere. You stop in a safe and reasonable manner and tow the car. The repairs are performed and completed, at least the cooling system repairs. Then, after the car was driven and made to do some work(which could be called normal operation) it overheated. If this seems accurate, then the repairs are not at fault. It is typically what happens, as I stated earlier. You are not at fault either, it is just what has happened, and you are responsible for the cost of the removal of the head and its subsequent repair.