North Carolina is poised for another radical overhaul of its mental health system. This time the changes have to do with the way state mental health agencies pay for patient care. A new law passed by the state General Assembly last spring requires agencies to become more like HMOs. Instead of billing Medicaid for individual services, agencies will get a lump sum up front, which they will then use to pay patient costs. Opponents of the legislation fear this change will lead to poor care for the state's mentally ill.