Welcome to the party. There are two homebrew stores in the Des Moines area, one is in Valley Junction and is not that great, but there is another store in West Des Moines that I just heard about called "Go Beer Crazy". Never been there because I had never heard of it before last week, but apparently they also have a large and exotic beer selection.
Otherwise the best place I have found to get homebrew supplies are midwestbrewsupply.com in Minnesota. They answer emails quickly if you have any questions.