My First Art Gallery...I'm so excited....Advice/Tips requested. PIOG

Last week, I was looking on Craigslist for PT or apprentice type jobs in photography.  I came across this listing  titled "calling all entries".  I was for a photography art show in Detroit, MI  (not far from here).  The theme was "Personification".  I sent a photo for consideration. I figured, it couldn't hurt. 

Well, the next day, I got an email saying that it was accepted and I needed to have it printed, framed and turned in in two weeks. She didn't tell me a size, she said its my choice, not too tiny and not too large.  Based on framing prices, I'm going with the size 12x18.

I have never had anything in an art gallery before.  Have any of you?  Honestly, I don't know anything about art shows or galleries.  If any of you have any tips, please let me know.  Is that size photo ok you think?  Are these shows generally to purchase the photos or is it just for show?  If for purchase, do I have to have a minimum price in mind?  I don't know how these work.

Anyway, here is the photo that'll be hanging up in the gallery November 14 through the New Year.

PS, if it looks familiar to some of you, you may have seen it for it's original purpose - a CM contest on personification. :-P