To prepare crust, combine crumbs, margarine, and sugar in a mixing bowl. Press mixture firmly into bottom of 9"x13" pan. Chill one hour, or until firm. Or, bake in a 350 oven for ten minutes, or until edges are brown. Cool on rack before filling. To prepare first layer, combine cream cheese and powdered sugar in a mixing bowl. Mix until fluffy. Fold in half carton whipped topping. Spread over crust. To prepare second layer, combine pudding mix, milk, and pumpkin pie mix. Mix until thickened and well blended. Pour over cream cheese layer. Top with remaining whipped topping. Chill three hours or overnight.