Preheat oven to 400°.
To prepare vegetable filling, heat oil in a large nonstick skillet over medium heat. Add leek, sage, and garlic; sauté 5 minutes. Add squash, wine, and water; cover and cook 20 minutes or until squash is tender, stirring occasionally. Stir in 1/4 teaspoon pepper and spinach.
To prepare sauce, place flour in a large saucepan, and gradually add milk, stirring with a whisk until blended. Place over medium heat; and cook until thick (about 10 minutes), stirring constantly. Remove from heat; add cream cheese, nutmeg, and 1/8 teaspoon pepper, stirring with a whisk. Combine cheese shreds and provolone cheese; set aside.
Spread 1/2 cup sauce in the bottom of a 13 x 9-inch baking dish coated with cooking spray. Arrange 3 noodles over sauce; top with 2 cups vegetable filling, 1/2 cup cheese mixture, and 1/2 cup sauce. Repeat the layers, ending with noodles. Spread the remaining sauce over noodles. Cover and bake at 400° for 30 minutes. Uncover, and sprinkle with 1/2 cup cheese mixture, and bake an additional 10 minutes. Let stand 10 minutes before serving. Garnish with sage sprigs, if desired.