1. Get an attorney
2. DO NOT repeat DO NOT call the plaintiff's attorney. Your attorney will do that for you.
The collection agency doesn't care how they get the money as long as, it is ASAP, on their timetable, not yours. They will hound you until they get the money.
At the same time, there has been discussion in the U.S. Congress regarding the practices of collection agencies, and their nature of threatening debtors.