PREHEAT oven to 300°F if using a silver 9-inch springform pan (or to 275°F if using a dark nonstick 9-inch springform pan). Mix graham crumbs, pecans, sugar and butter until well blended. Press firmly onto bottom of pan. Melt 5 of the chocolate squares as directed on package.
BEAT cream cheese in large bowl with electric mixer on medium speed until creamy. Gradually add sweetened condensed milk, beating until well blended. Add melted chocolate and 1 teaspoon of the vanilla; mix well. Add eggs, 1 at a time, mixing on low speed after each addition just until blended. Pour over crust.
BAKE 1 hour or until center is almost set. Run knife or metal spatula around rim of pan to loosen cake; cool before removing rim. Refrigerate 4 hours or overnight.
MIX pie filling and remaining 1 teaspoon vanilla; spoon over cheesecake. Melt remaining chocolate square as directed on package; drizzle over cherries. Let stand until firm. Cut into 16 slices to serve.