Hi Wicca Moon,
Wow, that's quite a bit of scar tissue. Had the original piercing become infected upon removal of the jewelry? This is kind of a difficult question. Not one I'm sure I can give you a definitive answer on.
Scar tissue is primarily composed of collagen. Collagen is fairly tough, relatively lacking in elasticity, and therefore will likely take a good bit more effort to pierce than normal skin. This is where it may become somewhat mixed...
Given the amount of scar tissue, it is likely much of the nerve tissue within may have died off due to a relatively poor blood supply. I would suspect the pain would be a good deal less, but probably not any worse. The down side to this is, if conditions aren't absolutely sterile, and bacteria did enter the wound, the poorer vascular innervation to this collagenous mass could make fighting infection particularly difficult. I would particularly worry about forms of Streptococcus or Staphylococcus. Just make sure, if you do go through with it, it is done by a very reputable and knowledgeable studio. As well, I would make sure your gall bladder scar is completely healed.
I do think it would be good to get a second opinion from someone else on here. Maybe you could message someone like J 9, as she is a nursing student, and very knowledgeable.
Anyhow. Please do be careful though. Take care.
