if it's caused by a hernia you may be OK. They can usually fix those when they do the sleeve.
actually, a lot of people worry that this is going to be really difficult (I did as well), but once you get used to it, it's not at all.
complications are pretty rare, actually. The most common one with sleeve is GERD, but that happens to about 30% and can often be managed medically. So 70% of sleeve patients DON'T have it.
although some people do have issues with diarrhea with sleeve (and bypass, too), constipation is WAY more common. You see diarrhea more with duodenal switch patients.