Necrosis is a scary word. Losing a small piece of skin is not usually significant after a large skin surgery. It will typically heal just fine with proper wound care. Extensive necrosis is another issue. You haven't mentioned the extent of your problem. Limit healing problems by staying warm, avoiding pressure, preventing infection with proper wound care and eating well to encourage proper healing.
Having skin necrosis after a skin resection procedure can happen but fortunately is not frequent. For most, it happens when there is a large undermining of the skin compromising the blood supply to the area or if it is closed on extreme tension. Is more common to see superficial necrosis along the wound but for most wound care should take care of it. Once healed, it can be re evaluated for revision of the scar if necessary. Hope this helps