I've only had a resection of the large intestine. A friend's son had extensive surgeries on both intestines and ended up with only a small section of the small intestine, though it was done little by little over several surgeries. But from those experiences I can say that your output will be more liquidy for a while (like, a couple of weeks) and then the body will adjust to reabsorbing the water through a shorter intestine and things return to normal.
You may have Depends for a little while, but the body is incredibly adaptable. My thoughts are with you that your upcoming surgery goes well!