Heat 1 tablespoon oil in a large nonstick skillet over medium high heat. Add celery and next 3 ingredients. Sautè 3 minutes or until tender. Transfer vegetables to a 5-quart slow cooker. Combine flour,gravy mix,and pepper in a large shallow dish. Sprinkle veal shanks with salt. Dredge veal shanks in flour mixture.
Heat remaining 1 tablespoon oil in skillet. Add veal shanks. Cook 3-4 minutes on each side or until browned. Place shanks on top of vegetables in slow cooker. Add tomatoes and next 3 ingredients. Cover and cook on LOW setting 9 hours or until tender. Serve veal with sauce over polenta.