1. Place ham on a large platter and bring to room temperature. Preheat oven to 325°F.
2. Remove skin and all but a 1/4-inch-thick layer of fat from ham; set ham fat side up in center of a large roasting pan.
3. In a small bowl, whisk preserves, mustard, sugar and vanilla until thoroughly blended. Brush half of peach preserve mixture over ham. Cover loosely with foil and bake for about 30 minutes, or until juices start to gather in bottom of pan.
4. Remove foil and brush on remaining peach preserve mixture. Bake, uncovered, until internal temperature on a meat thermometer reaches 140°F, 1 1/2 to 2 hours, basting every 15 to 20 minutes. If bottom of roasting pan begins to scorch, add 1/2 cup of water at a time and continue basting.
5. Transfer ham to a large cutting board. Cover with foil and let rest for 15 minutes. Cut ham in thin slices against the grain and serve.