Arrange taco shells in a shallow baking pan. Place in very slow oven (250 degrees) to crisp while making filling. Heat large skillet; crumble meat in and cook until browned, stirring constantly. Tilt skillet and spoon off excess fat. Stir in chili seasoning mix. Add corn, tomatoes, tomato sauce, onion and celery. Heat to boiling. Turn heat to low and cook, uncovered, for 15 minutes, stirring occasionally. Spoon into taco shells. Top with cheese and serve on crisp lettuce. Or the filling may be served like chili con carne, if you don't like taco shells.