Cook manicotti shells according to package directions. Meanwhile, in a 1 1/2 quart casserole, crumble ground beef. Cook, covered, on 100% power (high) for 2 1/2 to 3 1/2 minutes or till no pink remains. Drain off fat. Stir in refried beans, celery, and cumin. Fill cooked manicotti shells with meat mixture. Arrange the stuffed shells in a 10x6x2 baking dish. Pour corn and picante over shells. Cover with vented clear plastic wrap. Cook the stuffed shells on high for 8 to 10 minutes or till mixture is heated through, giving the dish a half turn once. Spoon sour cream over casserole. Sprinkle with green onions, ripe olives, and chopped tomato.