Thanks for your question. First, about re-baptism. In Acts chapter 19 we read of those who had received the baptism of John, but who had not been baptized as believers (nor had the Holy Spirit yet come upon them). These folks were re-baptized in the name of Jesus (Acts 19:1-7).
From the Book of Acts one would understand that every believer ought to be baptized. It is also clear that one is to be baptized as a believer. Other texts such as Romans 6:3ff. seem to indicate that every believer would have (or should have) been baptized as a believer. It is my conviction, therefore, that if one has not been baptized as a believer — even if they came to faith years earlier — they should be baptized.
There are also baptism studies on the BSF Website.
John Piper has some articles on Baptism on his Website.