Casual attire - seriously. We want folks to be as comfortable as possible. If you feel best wearing a suit, go for it. If you prefer a sundress (questionable given March, but you do you) go for it. Never worn a suit a day in your life? Rock those jeans. Please don't feel like you need to wear any one thing in particular.
Fridley is solidly in suburbia - it's where Annie grew up. That said, if you intend to do a lot of moseying about in Fridley or the immediate areas (all suburbs) you'd probably want a car. For hotels, we would recommend Roseville, MN. Still suburbs but there are a few Marriott/Hilton options. If you don't care about being near Fridley, it would not be unreasonable to stay in Minneapolis proper. If you are downtown you'll be able to walk around much easier (be sure to use the Skyway system). Expect to take 15-20 minute-ish cab/Uber/Lyft ride.