Preheat the oven to 325 degrees F. Mix together the preserves and mustard in a small bowl and set aside.
Score the surface of the ham in a diamond pattern, about 1/8 inch deep. Bake according to the package instructions, 2 1/2 hours or longer. About 30 minutes before the cooking time is up, remove the ham from the oven and brush the glaze onto it. Cook until it's nice and glossy. Repeat with another layer of glaze if desired.
Serve the remaining glaze in a dish alongside the ham.