Changeling you asked:
"If I do not renounce my atheism, repent and start believing in and worshipping the christian god, what will happen to me?"
Changeling, if you are RIGHT and there is no God, you can answer that question easily yourself.
If you are wrong, you just have to accept the potential consequences. Maybe, if there is a God, he is merciful too.
I am not in any church, nor will I ever be. Maybe we are in the same boat.
Brant