Cook macaroni according to package directions, omitting salt and fat. Drain and set aside.
Coat a medium nonstick skillet with cooking spray; place over medium-high heat until hot. Add green pepper, celery, onion, and chicken broth; saute over medium-high heat 3 minutes or until vegetables are tender and liquid evaporates.
Combine vegetables, macaroni, cheese cubes, and next 6 ingredients in a large bowl, stirring well. Transfer to a 1 1/2-quart baking dish coated with cooking spray. Bake, uncovered, at 325° for 20 minutes. Sprinkle with breadcrumbs and paprika; bake an additional 10 minutes or until thoroughly heated.