M.I.
We're in the process of selling ours in a short sale now but since ours is an 80/20 loan it's a little more complicated. Just know that it takes foorrreevveerr! We listed it in October of last year but we listed it at breaking even point, no luck, so the realtors that we had finally realized that we would have to do a short sale (even though before we signed with them I brought it up to them numerous times). So then they "supposedly" had an investor but they wanted us to pay $999. out of pocket for the "extra work" involved in a short sale. We backed out and found another realtor who was not charging extra (they do get paid commission from the bank). She's even throwing in some of her commission to help the deal go through. Also you do need to have some kind of hardship so you'll need to submit a hardship letter, and a whole bunch of other stuff, kind of like you're applying for a loan. In order to qualify your house must be under market value. Oh, and then the bank may want to try to come after us for the difference in which case we'd have to file for bankruptcy. They also send a 1099 at the end of the year but I'm not sure if/how much that will affect your taxes.
So basically be prepared to wait a long time (we're lucky the buyers haven't backed out yet), make sure you get a realtor experienced in short sales and who won't charge extra, and be prepared for a lot of paperwork. Good luck!