Short Sale: Attorney negotiation vs. Realtor negotiation?

[J G]

Hi there,
I have a property that is rented out (because I wasn't able to sell before) and am looking to start the short sale process. I was wondering if any one had any advice regarding my situation.

The main question is based on whether or not I should hire an attorney for $500 flat fee to work / negotiate my short sale... or save the money and work with my realtor who has experience with short sales.

Is there value in having an attorney involved? Does it get me a better chance at successfully navigating and expediting the process?

(Some more details: I am current on the mortgage but only because the tenant offsets some of my loss. The tenant is moving out so time is very important. I know that being current does not provide the best leverage.)

Thanks for your time and help,
JD