My son overheated My 1996 Chevy Cavalier, 4 cylinder. He put in cold water right away. It would not start. It sat for a week and it started. I notice the water pump weep hole was leaking. So I replaced the Water Pump and thermostat. Fill it coolant, try to start and it did not. Pulled spark plugs and found water in all four cylinders is this head gasket or warped head. If it’s the Head can it be milled down or should I get a new one.