The Two sum up, not replace, the Ten, for James said 30 years after the Cross that adultery and murder were still sin. "Covenant of Grace", along with "The Two replace the Ten", are two phrases that are used to advance the false narrative that we are now at liberty to break the Ten Commandments that God writes on New Covenant Christian hearts. When you get down to it, Christians don't have a problem with 9 of them, it's just that fourth one - to the point that they will even argue that we are free to keep doing what made necessary the death of our Lord. Jesus has shocking words in the last day for those who believe and teach that we can erase what the Holy Spirit writes on the hearts of New Covenant Christians (Matthew 7:23).
Proverbs 10:12 (NASB)
Hatred stirs up strife, But love covers all transgressions.
1 Peter 4:8 (NASB)
Above all, keep fervent in your love for one another, because love covers a multitude of sins.
Hello? If you are loving those whom you are instructed to love, you WILL NOT break the 10 commandments.
Oh and the 10 commandments do not encompas the entire law. There are 613 mitzvot or laws, not just 10.
http://www.jewfaq.org/613.htm - this will take you to a complete list and trust me, no one is keeping them all.