I would first seek a realtor who is knowledgable in short sales (there are quite a few out there nowadays). Depending on your mortgage company and how many mortgages you have, will often determine your success rate for completing a short sale. For example, I had a client that was interested in short saling her home. However, it took the mortgage company so long to review each offer that was submitted that the potential buyer would get frustrated and withdraw the offer. Another client had two mortgages and the second mortgage would not agree to accept the conditions at all - that client ultimately filed bankruptcy in order to surrender the home and not have any liability with the second mortgage.
I have had a number of clients successfully short sale their home so it is possible. Another option (if you only have one mortgage) is a deed in lieu of foreclosure. If you are interested in doing that, you would have to contact your mortgage lender directly and ask what the requirements are as each lender is different. What happens is that you end up simply surrendering your home directly to the lender, skipping the whole foreclosure process, and the lender waives any liability for the unpaid balance. Your credit report will reflect the deed in lieu of foreclosure (or short sale for that matter).
Good luck!