Place the cornmeal in a medium saucepan. Gradually add milk, stirring with a wire whisk until blended. Bring to a boil; reduce heat to medium. Cook, uncovered, 2 minutes, stirring constantly with a wire whisk. Remove from heat; stir in margarine. Set aside.
Combine sweet potato and next 6 ingredients (sweet potato through eggs) in a large bowl; stir until well-blended. Gradually add cornmeal mixture, stirring constantly. Pour sweet potato mixture into a 1 1/2-quart casserole coated with cooking spray. Bake at 350° for 40 minutes. Let stand 10 minutes before serving.