I learned some contemporary Christian songs to play at our church. For the songs (one of them was a Chris Tomlin song) I was able to find youtube videos that helped me out.

If you can already play folk well (strumming chords) I think it would really just be a matter of learning the chords and the structures of the songs.

A way to branch out from "just strumming chords" is to look at adding ornamental notes and some arpeggiation of chords. A typical one would be hammering on and pulling off the 4th note on the open D chord. You tube has some interesting videos on this...there maybe some lessons here too. For myself, I kind of stumbled on it on my own.