Cook spaghetti in large saucepan as directed on package, omitting salt. Meanwhile, heat 1 Tbsp. dressing in large skillet on medium heat. Add shrimp, scallops and 1/4 tsp. crushed red pepper; cook 3 min. or until shrimp and scallops are lightly browned, stirring frequently. Spoon shrimp and scallops into bowl; cover to keep warm.