As I continue in my own study of this important subject...questions arise. This is a subject where it is easy to propagate answers, but I think we are better off not to be dogmatic (and, oh boy, I used to be), but be students, learners. There are indeed so many things that happen when we come to the point of baptism -- many that we do not have the maturity to understand at that point, (including "forgiveness of sins" and "receiving the gift of the Holy Spirit" -- both part of the "formula" described in Acts 2:38-39...and this, not to mention "repentance" and "confession"). At times, some have treated baptism as some sort of end of the road after a disciple has been "taught" everything that he should know. For these, baptism has been a law to fulfill the requirements of certain passages...which is not much different than what we see regarding Old Testament theology and practice. There must be more to it than this. We need to consider Apollos. As much as he already knew about "the Scriptures" and about God, he was surely in for a spiritual rebirth and for a totally new experience when he received Christian baptism (cf. Acts 18).
I believe baptism is, more so, the beginning of our journey. It is a truly spiritual event in every way. La Gard Smith calls it "the believers wedding ceremony" -- a fitting description, I believe. How much can we know at baptism? (How much does a baby know at birth?) We barely understand the elementary things, but certainly not the deep things of God; these are revealed over time by the Holy Spirit. And how do we qualify or quantify His work? We cannot...it is discerned and appropriated by faith. This is a significant part of what comprises the heart of the new covenant. We do grow in our understanding of critical principles as we walk with the Lord. Consider the disciples as they became the apostles sent out with the mission of Jesus (Acts 1-2). The Spirit came and illuminated their minds and their eyes were opened to the experiences they had had with Jesus. He does the same for us as our Helper (John 14-16), if we are open and willing to study as we walk with Christ over the course of our lives.