Perhaps the surgery has to remove the blocked portion and reconnect the j-pouch, so the surgeon may want the pouch to heal for a bit. Or some other reason that would cause the j-pouch some needed rest. Every time I had problems I needed a temp ileostomy.
Since you've had an ilesotomy before, my guess is that it was a temp loop ileostomy and I would think you'd be getting that again. Only real question I'd want to know is how long before the takedown. You won't have to worry about diet at all- ileostomies have less trouble since you have total control of emptying the contents. I believe the temp loop ileostomy is more prone to bag leaks than the end ileostomy, so you'll probably be changing your bag every 3 days or so. At first you'll be using bags that you have to cut the opening because your stoma size shrinks after surgery. Once it's done shrinking , if you're having trouble with leaks try a bag that has a convex wafer to it. The convexity helps when the stoma is short. If you have any questions about the bags you'll wear, call the product manufacturers directly. They all have ostomy specialists you can talk too. These specialists know more about taking care of the bags than nurses and love to send out free samples. Hope all goes smoothly!