Hi goldie, I'm not sure about the timing, but many plastic surgeons offer free consultations and would be able to give you an idea. I've heard that you're supposed to wait about a year after your weight has stabilized.
I've heard of a doctor in the Richmond, VA area (I know that's not exactly DC), but he has minimally invasive body lift/contouring procedures that offer much quicker recovery time, less scarring and I think they are less expensive. As you begin to meet with doctors, it may be worth making the trip to meet with him. Here is a link to his website:
Dr Bermant's Background and CV Plastic surgery, aesthetic, and cosmetic surgery
I live in the Kansas City area and I'm hoping to find someone who does the same type of procedures closer to home.