Donna,
Once you are healed from the surgery, there is no reason you cannot resume bodybuilding. The combination of Gilbert's Syndrome and thal minor does lead to gallstones, and it may be that you have a stone lodged in a duct that is causing the pain. The spleen size is unusual in thal minor, but not unheard of, as minors do often have enlarged spleens, but not of that magnitude. But it does happen due to a high rate of red blood cell turnover or hemolysis. Regardless of the cause, the description you've provided of your spleen size presents a spleen that is in danger of rupture from a sharp blow.
Once you have had a splenectomy, you want to guard against clotting issues and pulmonary hypertension (PHT or PAH). Natural vitamin E complex can help you avoid the clotting issues. L-carnitine or L-arginine supplements can help you avoid PHT. If you've been bodybuilding, you may already be taking this. Think antioxidants, both supplements and diet. The high rate of hemolysis leads to a high rate of oxidation in the body and this must be countered to maintain good health.