Russ, I urge you read the New Testament. There you will find answers to your questions on life before Christ and after Christ. The law that you are referring to (circumcise on 8th day) was only meant to last until Christ fulfilled the law. As Paul tells us, after the law had been fulfilled, we are free from it.

Paul tells us that the law was there to help humans know what sin was. He also tells us that circumcision represented a physical covenant with God in a time before the law had been fulfilled. After Christ, and the law had been fulfilled, what matters for Christians is circumcision of the heart. Paul did not teach the need for circumcision, and it was a defining chracteristic of early Christians that they did NOT circumcise. It's was a sign of our liberty in Christ.

As Paul tells us, if you place any worth on the law, then you have to fulfill all the law - as the Jews try to do. And if you try to put yourself right with God through the law, you are effectively denying what Christ did. Therefore, those who believe circumcision is necessary are Jews, not Christians.