While I have not yet had my bariatric surgery, I have had three open abdominal procedures for other reasons. All three went through the same area, from just above my belly button to just below my belt line (below my muffin top) in my upper groin. The first one was not bad, since my skin was just skin and not scar tissue like it is now. The first one was in 1995 and they sewed it internally and stapled the outside closed. The second and the third were last year, in May 2017 and in August 2017. The one in May was mostly healed when the surgeon had to open me back up again through the same place. The one from August 2017 took over four months to heal.
As for pain, the first one hurt the most of the three (but it was still tolerable with pain medicine) because it was on virgin skin. The second and third did not really hurt much because scar tissue usually does not have as many nerve endings in it.
You will likely have what is called a "wound vac" installed over the incision dressing after they close you in the operating room. This is a dressing covered with sponge material and adhesive-backed plastic wrap with a tube going from the dressing to the wound vac. It looks like Saran wrap, sort of, but it is a bit thicker. What this device does is keep a constant negative pressure on the wound to draw out any fluid and blood, which if left to pool within the wound could cause an infection. The wound vac does not hurt at all and really speeds up the healing process. When I had my surgery back in 1995, wound vacs were not widely used and I did not have one. Both surgeries last year used them. The wound nurses will change the dressings every couple of days and depending on how long you stay in the hospital, you may be sent home with a portable version of the wound vac. My surgery in August last year did just that. I had to carry the wound vac with me everywhere I went, but it was small and rechargeable and not very intrusive. After a while, I forgot it was even there. I had to come to the hospital wound care clinic every three days to get my dressings changed and I had the portable vac for two months. I was in the hospital for over three weeks so overall, I had the wound vac for almost three months.
It sounds much worse than it is, believe me. I did not have the choice for any my surgeries either.