Last year, when I too lived in MN, I went to Eagle Mountain to go snow boarding the first time. It was sooo much fun, but very difficult to get going. I honestly don't have that many tips for you, but just don't get discouraged! I think the hardest part is to get back up after you fall, but you can always unhook your boots to get up and then hook them back in. If you fall, don't put your hands out! Snowboarding is the #1 way people break their wrists. I had a lot of fun, I'm sure you will too! Once you figure out how to keep your balance and get up after you fall, it's pretty smooth after that. And if you want to learn to stop, at the end of the hill when your going pretty slow, do a kind of sharp turn and face forward. I learned to stop that way, I fell over quite a few times though trying to. lol!
Some people have told me snowboarding is soo much harder than skiing, and some have told me it's so much easier! I guess it just depends what your strenghts are... if you have good balance, maybe snow boarding will be easy to pick up!

Well, I'm sure you'll have fun & good luck!