STIR boiling water into dry gelatin at least 2 min. until completely dissolved. Refrigerate 1-1/2 hours or until slightly thickened (consistency of unbeaten egg whites).
BEAT yogurt and dressing in medium bowl with wire whisk until well blended. Gradually add gelatin, beating until well blended. Gently stir in whipped topping.
POUR into crust. Drizzle with preserves; cut through whipped topping mixture with knife several times for marble effect. Refrigerate 4 hours or until firm. Store leftover pie in refrigerator.