Hello:

You picked a great year to head to South Dakota, the birds are abundant. As far as your first time going, make sure you bring a very comfortable pair of walking boots, water proof if possible. And make sure you have good brush pants. Other than that, make sure that you bring both warm and cold weather clothing with you. I have been out there in great weather, and weather so cold and blustery that you wish you get warm. As far as your shotguns go, you probably wont need a shot extender if you are a good shot, and bringing a backup gun is a great Idea. I don' t know what kind of hunting you are planning to do, but if you are bringing your dog, I suggest a 5 gallon jug of water so you can have it all day to give you dog the water he needs.
Where are you hunting, and what week are you heading out. Just curious.
I am from Wisconsin as well, and I can promise if you do your research or go with an experienced group, you will get birds.
Have a great hunt.

Bill (Wi)