How did the writings of the NT come to be?

[Drich]

He started a church where?

Rome, corinith, Galatia, ephusus, and everywhere inbetween
http://www.matthewmcgee.org/paultime.html

And why isn't that one of the "leading churches"?

Because theri isn't 'One form/denomination of christianity.'

Who's to say he didn't draw inspiration for those writings from himself?

God.

The account itself states:
[quote="http://en.wikipedia.org/wiki/Paul_the_Apostle"]while traveling on the road from Jerusalem to Damascus on a mission to "bring them which were there bound unto Jerusalem", the resurrected Jesus appeared to him in a great light. He was struck blind, but after three days his sight was restored by Ananias of Damascus, and Paul began to preach that Jesus of Nazareth is the Jewish Messiah and the Son of God.

What would you think of someone who would claim such a thing today?
hint: Van Gogh.

Would you trust them?

It completely depended on what he had to say.

I know, I wouldn't trust their mental sanity.

That is because you have aligned your value system on what you peers tell you is ok, rather than going out on a limb and judging for yourself.