2001 Chevy Trailblazer Please Help!

Smells problem
2001 Chevy Trailblazer 6 cyl Four Wheel Drive Automatic

I took my car to Auto Zone to find out what was the smell going on in my car. It smells like fish. She told me that the antifreeze was leaking and if I didn't get it fixed soon it could cause Carbon monoxide poisoning because I could smell it inside the car. She directed me to a mechanic down the road and he told me I had a crack in the radiator. He replaced the whole radiator but I still smelled the fishy smell. He began to tell me that I need to flush the radiator because it will still smell at worst. Now my car is overheating! What should I do next?