My 92 735 il 168,000 miles lost a fan belt and over heated for brief time. Three weeks later it developed an antifreeze leak from the head gasket just above the engine block plug. I put in some radiator sealant. The leak stopped but I have intermittant white smoke.. I suspect is leaking into the engine.. What should I do? ignore? replace head gasket and do valve job at same time, or get a new engine? My wife wants a new car..Any suggestions Is it hard to replace head gasket? Thank you