Bring Dr. Pepper, sugar, orange juice and mustard to boil in medium saucepan. Reduce heat to medium-low and simmer until mixture is syrupy and measures 1 1/2 cups, about 8 minutes and let cool.
Remove Ham from packaging and discard plastic disk that covers bone. Place ham in plastic oven bag (or foil), tie bag shut, and trim excess plastic. Set ham cut side down in 13x9 inch baking dish. Cut 4 slits in top of oven bag if used. If using foil, place ham cut side down in baking dish and wrap tightly. Let stand at room temp for 1 1/2 hours.
Adjust oven rack to lowest possible position and heat oven to 250 degrees. Bake ham until center registers about 100 degrees on instant read thermometer, 1 1/2 to 2 1/2 hours, depending on weight of ham.
Remove ham from oven and roll back sides of bag to expose ham. Brush ham liberally with glaze and return to oven briefly until glaze becomes sticky, about 10 minutes. Remove from oven, brush entire ham again with glaze, loosely cover with foil and let rest for 30 to 40 minutes before carving.
*Flavor is better when soaked through the ham for a full day in fridge and reheated. Recommend also making an extra side of glaze to heat up and place on ham as a "dressing" for more flavor.