here is what i think. He got the wrong head on it. He got a one oil port for a two oil port block. The fluid interchanged and well you got a heck of a mess. But could be wrong and he didnt tighten the head bolts correctly and it blew the gasket. You have to torque it in sequence and then when you finished it has to be dial torqued to a specific degree. Ask him what degrees he had to torgue it too and if he doesnt know then you have him telling you a lie.