Yes, the port site is the largest incision. I was banded on November 19th, and it took about a week and a half for the gas pains in my shoulder to go away, but using the heating pad and getting up and walking around for short periods of time as often as possible REALLY helped. It also took about 6 to 7 days before the tightness in my stomach went away for the most part (which is dead on for what the doctor said, he told me I would feel better Saturday and my operation was on Monday), but I again found that getting up and moving around as much as possible REALLY helped that dwindle away as the days went on.
As far as sitting comfortably, I usually carried a pillow around with me when home to help support my back and allow me to sit more comfortably. Also, when going anywhere in the car, I brought one pillow for behind my back, and one to keep pressed to my stomach for the trip so that things wouldn't get jostled around too much on bumpy roads!
Good luck with the coming days and I hope you start feeling much better soon!