Cook manicotti shells according to package directions. Meanwhile, in a 1.5 quart casserole, crumble ground beef. Cook, covered, on 100% power (high) for 2.5 to 3.5 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.