A question towards Jews who reject Christianity?

I'm not accusing you or asking why, but I have a question. Is Judaism only for ethnic Jews? Assuming they will goto Heaven with God. The theme of the Gospel in Christianity is ultimate salvation through Jesus Christ to receive eternal life with God, to all nations of all the world. That's nice. But is Judaism really closed towards only for jewish people? In other words, i'm asking will only Jews goto Heaven with God, and I know God doesn't use favoritism on any body, whether jew or gentile. So do I have to convert to Judaism? Am I allowed? my etnicity is 100% korean. What is the message of salvation for mankind in Judaism, apart from Christianity?