Combine all marinade ingredients in a large ziptop bag. Add pork loin and refrigerate for 2 to 12 hours.
Preheat oven to 325 degrees. Remove pork from marinade, reserving the marinade.Place pork, fat side up, in a roasting pan.
Roast until pork reaches an internal temperature of 145 degrees. This can take from 55 to 80 minutes, depending on the size and thickness of your pork loin.
While the pork is roasting, place reserved marinade, peach preserves, and chili sauce in a small saucepan. Add 1/4 cup of water and bring to a simmer. Keep warm.
When pork is about 15 minutes away from being done, baste it with the glaze.
When pork is done, set it on a cutting board or serving platter and let it rest for 15 minutes before slicing. Pour any juices from the roasting pan into the saucepan with the glaze. Reheat the glaze if necessary and serve it with the pork.
Notes
Dry white wine or apple cider can be used instead of dry sherry.To make the glaze a little spicy, add 1/2 teaspoon of crushed red pepper flakes.