Check the papers or at a good sporting goods store and see if they have any used 870's. I also think there are a few sporting clays/ trap/skeet ranges around your area. Those guys can be quite helpful and many times somebody has a license to sell guns. That could save you a few bucks and usually 870's are so tough that a used one is just as good as a new one.

What about the Cabela's in Owatonna? You aren't too far from there. The also have a used gun section. If you've never been to that store it is absolutely worth going regardless if you are buying a gun or not. Check out the mount of the three lion's attacking a zebra, it is almost scary how real it looks.