i have a 2007 push start nissan altima . my car ran hot on me twice before i recieved the news that i had a blown head gasket. i have only had my car four months however it was used. what should i do

car ran hot when leaving work four hours after it had initially ran hot , I imedietly pulled over and had my car towed to my mechanic, he informed me my radlator was cracked. he repaired it and it wouldn't start and when it did it puffed white smoke and leaked water from the engine signaling im assuming a blown head gasket. I was told I would need to purchase an engine, but my father instructed me to have my engine rebuilt being that it would be a better and cheaper solution. im so lost I don't know much about cars but I don't want to loose my car. it is paid for and I cannot afford car payments right now