What did Paul do after his conversion before the Gospel of Grace came out?
After his conversion, Paul went out to a three-year seminary training in the desert. Only after that period did the Gospel of the Grace of God come out. This preparation preceded his ministry, and the context places it before the distinct message for the Church, the Body of Christ.
Les explains that after Paul's conversion, the Lord said He would show him how great things he must suffer for His name's sake. From that point on, Paul goes out to a three-year seminary training in the desert, and then out comes the Gospel of the Grace of God. Les contrasts this with the earlier situation that was probably Jew only with some Gentile exceptions. Now God is pulling out another group, the Church, or the Body of Christ, which is not exclusively Gentile but mostly Gentile, with some Jewish adherents.