Bariatric surgery is not directly related to the presence or absence of the thyroid gland. however hormones produced by this gland directly interfere with the metabolism, so you should always be followed up by your endocrinologist and so have adjusted according to your weight and need dose.
It should not be a problem having the tummy tuck surgery with a lap band port in place. The more information you are able to provide to your plastic surgeon the better. The position of the port often needs to be adjusted during the procedure; sometimes the port is more palpable after the tummy...
If the realize band is fine and not causing problems, you can leave it alone. if it needs to be replaced for any reason, it would need to be replaced with an apollo lap band, or you would need to be converted to an alternate weight loss surgery to maintain weight loss. but in and of...