Cook shells in boiling, salted water for 8 to 9 minutes until just al dente. Drain and rinse.
Mix next 5 ingredients and stuff shells.
Put 1/2 sauce in bottom of baking dish. Arrange stuffed shells in a single layer in dish. Place remaining marinara sauce over top and sprinkle with mozzarella cheese; cover loosely with foil.
Bake at 350 degrees for 20 minutes, remove foil and bake an additional 10 to 15 minutes until mozzarella is melted and pasta shells are tender.