STIR boiling water into dry gelatin at least 2 min. until completely dissolved. Refrigerate 1-1/2 hours or until slightly thickened.
BEAT yogurt and dressing in medium bowl with whisk until blended. Gradually add gelatin, beating until blended. Gently stir in COOL WHIP.
POUR into crust. Drizzle with preserves; cut through COOL WHIP mixture with knife several times for marble effect. Refrigerate 4 hours or until firm.