I won't get detailed here in the event you would need explanations for everything. In GENERAL, double jaw surgery:
* A Lefort 1 to; advance out your upper jaw, drop down your upper jaw for more tooth show from the front, widen your upper jaw to the sides. It most likely could be a 3 piece lefort requiring some grafting material. All those things would improve, not only your smile but also the retrusion you have to the maxilla.
* What ever has to be done to the LOWER JAW to balance with the upper jaw which in general is a BSSO.
* What ever orthodontic preparation needed before hand in order to get a jaw surgery.