Place lamb cubes in large resealable plastic food storage bag. Combine mint, salad dressing, 1/4 C. Frank's Red Hot Sauce, Worcestershire, fennel seeds and garlic in small bowl; mix well. Pour over lamb. Seal bag and marinate in refrigerator 1 hour.
To prepare Yogurt Sauce, combine yogurt, cucumber, 1 Tbs. Red Hot Sauce and garlic in small bowl; set aside.
Thread lamb onto metal skewers, reserving marinade. Place skewers on grid. Grill over hot coals 10-15 minutes or to desired doneness, turning and basting often with marinade. (Do not baste during last 5 minutes of cooking.) To serve, remove lamb from skewers. Place lamb in pita bread halves. Top with tomatoes, onions and some of the Yogurt Sauce. Garnish as desired.