What do you suggest if my dad has a loop colostomy, and is hoping to reverse it. how easy or hard is the reversal procedure?

Very simple: Various procedures are used to divert the bowel, in particular when a low surgical resection of the sigmoid colon is performed. Here the anastomosis is given a chance to heal by diverting food from the suture line. Loop colostomy has an opening on top of the loop which is repaired, the adjacent tissue opened so that the closed bowel can be dropped into the abdomen.