Yes, I do trail ultras. The Superior races are great. Great RD and very well organized. Make sure you learn how to hike fast - as you know there's lots of elevation change. You'll run, but expect to do some fast hiking too. Hill repeats and weighted runs are your friends. You probably know this but unless you're young and run 60+ miles per week, expect to go slower. If you've been a road runner you can expect add anywhere from 2-5+ minutes to your per mile time. This is not scientific, but sometimes people are surprised and it can get hard to get around mentally. The trails are rough and generally muddy. Everybody goes slower. I've done the 100 miler 2x (full disclosure I DNF'd at 50 and 85 miles due to medical issues). Gonna get that beast done someday.
Check out Marquette Ultra races as well
here They're very scenic and many folks run those in prep for Superior. I've done the 50 mile 2x up there.
here If you're on FB join the Midwest Trail Runners page. It's a great, supportive group of people and you'll find many local group runs and races regularly posted. People there also have a wealth of wisdom and advice. Otherwise google UMTR (Upper Midwest Trail Runners). That group is also great for info and hosts races.
Happy trail running. It's very addictive.