Agreed that you can do it and we all have. Not only should you have water ready for a water change within a couple of days or if you have a spike, but I would also suggest 20% water changes three or four times in the following two weeks. I'd also suggest plenty of fresh carbon.
If the sand in your 29 is at all established, I urge you to consider using new sand in your 55 or thoroughly washing the sand in your 29 before using in the 55. Established sand tends to contain things you don't want released to the water column. Besides, using new sand makes the transition easier.
Be sure you water test the 55 and whatever circulation system you're going to use for several days. Just use tap water for this. Since it's a used tank, you want to be sure there are no leaks before you make the move.
I would also offer this general statement about the aquariums you're using. The 29 and 55 are in a group of tall, relatively narrow tank shapes. They offer a good frontal display but are generally more difficult to keep because the sand and water surface areas are relatively small in relation to the water volume. As you look to the future, consider lower/wider aquarium shapes. For example, a 40 breeder is much easier to keep stable than a 55 because it has considerably more effective surface area. You'll find that to be the case with all of the "breeder" shaped aquariums. That's why, in the 100-gal. range, you'll find most people migrate to the 120. Just something to think about.
Gary
