Spray 3 1/2- to 4-quart slow cooker with cooking spray. In medium bowl, mix stuffing mix, celery, onion and poultry seasoning. Stir in broth to moisten. Stir in cranberries.
Spoon half of stuffing into slow cooker. Sprinkle turkey with salt and pepper; place over stuffing. Spoon remaining stuffing around turkey.
Cover; cook on Low heat setting 8 to 9 hours.
About 15 minutes before serving, remove turkey from slow cooker; keep warm. Stir stuffing and cooking juices until mixed. Cover; let stand about 10 minutes. Meanwhile, in 1-quart saucepan, heat gravy.
Cut turkey into serving pieces. Serve with stuffing and gravy.