Funny, I have exactly the same story as the OP. I once uploaded an original composition to a guitar forum (probably this one), and it was compared to Mr. York. I checked him out, and became a huge fan. Sunburst and Sunday Morning Overcast have been in my repertoire, off and on, for the last 10 years.
As noted, York is one of the founding members of the LA Guitar Quartet (along with Scott Tennant, by the way). I don't know if he's a full-time guitar or composition professor, as some of his LAGQ colleagues are. I think I read somewhere he has a degree in jazz composition.
I do know that he has tons of solo recordings, and a great number of his pieces have been published. If you want to hear even more, pick up just about any LAGQ album and you'll find some of Andy's compositions. He's also got a website with music samples, concert dates, etc.