Paul was a Jew, probably a Rabbi, died around A.D. 64 exicuted by the Romans under Nero. He was born in Tarsus a city in Asia Minor (Turkey) raised a jew and Roman citizen meaning he had a cosmopolitan cultural backgrond and was well educated. He is known to have studied under the famous Rabbi Gamaliel. He began persectuing the chruch then had a radical conversion experince invovling a light and a voice speakign to him claiming to be Jesus on the Road to Damacus. Most of this we know from the New Testament. Scholars strongly support his historicity. Several of his letters in the New Testament are universally accepted by scholars as genuine.
The primary source is his own letters. Of these, Romans, I and II Corinthians, and Galatians are indisputably genuine. Most scholars also accept Philippians, I Thessalonians, and Philemon. Opinion is divided about Ephesians, Colossians, and II Thessalonians. The Pastoral Letters (I and II Timothy and Titus) are held by many scholars to have been written considerably later than the time of Paul. The story of Paul's conversion and missionary career is given in Acts, probably written many years after his death. Some sections dealing with sea journeys may be derived from the diary of a companion of Paul. Traditionally this was thought to be Luke, the evangelist and author of Acts, a view still held by a number of scholars.Ignatius of Antioch (35-110) mentions Paul by name in his own letter to the Ephesians. "Ye are initiated into the mysteries of the Gospel with Paul, the holy, the martyred, the deservedly most happy, at whose feet may I be found, when I shall attain to God; who in all his Epistles makes mention of you in Christ Jesus. " Scholarship almost unanimously regards Paul as historical and sees him as the primary evidence for Jesus' historicity.
(1) Contemporary critical scholars agree that the apostle Paul is the primary witness to the early resurrection experiences. A former opponent (1 Cor. 15:9; Gal. 1:13-14; Phil. 3:4-7), Paul states that the risen Jesus appeared personally to him (1 Cor. 9:1; 15:8; Gal. 1:16). The scholarly consensus here is attested by atheist Michael Martin, who avers: "However, we have only one contemporary eyewitness account of a postresurrection appearance of Jesus, namely Paul’s."Paul also quotes sources earlier than himself that take us back to the early days of the Christian movement. These sources are form the Jerusalem chruch in the form of creeds. They document the understanding of the earliest Chrsitians.
In addition to Paul's own experience, few conclusions are more widely recognized than that, in 1 Corinthians 15:3ff., Paul records an ancient oral tradition(s). This pre-Pauline report summarizes the early Gospel content, that Christ died for human sin, was buried, rose from the dead, and then appeared to many witnesses, both individuals and groups...Critical scholars generally agree that this pre-Pauline creed(s) may be the earliest in the New Testament. Ulrich Wilckens asserts that it "indubitably goes back to the oldest phase of all in the history of primitive Christianity." Joachim Jeremias agrees that it is, "the earliest tradition of all." Perhaps a bit too optimistically, Walter Kasper even thinks that it was possibly even "in use by the end of 30 AD . . . ." 
examples of creedal forms:
1 Corinthians 15:3-8 has long been understood as a formula saying like a creedal statment.
For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;
1Cr 15:4 And that he was buried, and that he rose again the third day according to the scriptures:
1Cr 15:5 And that he was seen of Cephas, then of the twelve:
1Cr 15:6 After that, he was seen of above five hundred brethren at once; of whom the greater part remain unto this present, but some are fallen asleep.
1Cr 15:7 After that, he was seen of James; then of all the apostles.
1Cr 15:8 And last of all he was seen of me also, as of one born out of due time.
Two problems: (1) Doesn't conform to a canonical reading; (2) seems to contradiction the order of appearances of the epiphanies (in fact doesn't even mention the women). Nevertheless it is in general agreement with the resurrection story, and seems to indicate an oral tradition already in circulation by the AD 50s, and probably some time before that since it has had tome to be formed into a formulamatic statement.
Helmutt Koester theorizes that Paul had a saying source like that of Q from which he takes sayings that mirror those of the gospels. I have prepared a chart that illustrates these references.
Paul met James and Peter on more than one occasion. He records their meetings in his Letter to the Galatians.1:18
"After three years I went up to Jerusalem to get aquatinted with Peter and stayed with him fifteen days. I saw none of the other Apostles--only James the Lord's brother....(2:1-2)
Fifteen years latter I went up to Jerusalem this time I took Barnabas along and Titus..."
On that trip Paul laid out for the church leaders (presumably some other apostles as well ) the basic Gospel he had been preaching. In chapter 2 v11 he tells of another meeting with Peter in Antioch. On that occasion there was friction with Peter over Paul's inclusion of the Gentiles and Peter's hypocrisy in not accepting by refusing to eat with them. But on the previous two occasions they had accepted Paul's message of Grace to the gentiles. (see Jesus Puzzle page 2)
One is struck by the absurdity of Paul meeting three separate times with major principles of the events described in the Gospels and yet secretly they are thinking "O boy do we have him fooled! We made all this up, and this jerk believes it all, ahahaahah!" The first time he stayed with Peter 15 days, the second time he met with all the major church leaders (the church counsel described in Acts). What were they thinking? "Let's make up some more good stuff to tell this guy."
Than to understand that they all worked in poverty and hardship, never gaining anything, and died for their hoax, their plot in the preverbal smoke filled room? If there were no connection to Peter and James, and other Apostles, it might be easy to dismiss them as fictional characters and to think of the events of the Gospel as just myth. But knowing that these men were alive, living in Jerusalem, and running the church, at the same time that the stories which would latter become the four Gospels were circulating, one wonders why they would either go along with such absurd legends, or why even foment a plot to spread them? Why would they not denounce them and put a halt to them?