Friends 2001 Chevy Malibu was overheating and was driven on into the red. I replaced the thermostat for her hoping for no further damage however upon restart and drive the car now blows white smoke, runs rough as if a piston misfiring, and still overheats. I'm thinking HG, warped head, cracked IM, or cracked block etc. I just need to know what you think? Most of all is how to diagnose correctly. Thank you in advance.