Preheat oven to 350°.
Cook pasta according to package directions, omitting salt and fat. Drain and rinse.
Combine ricotta cheese and next 7 ingredients in a medium bowl, stirring well. Spoon mixture evenly into pasta shells. Place shells in an 11- x 7-inch baking dish coated with cooking spray. Spoon marinara sauce evenly over shells. Bake, covered, at 350° for 20 minutes or until thoroughly heated.