What does it take to get into a National Guard Special forces unit? What steps would I have to take to get there?

You can enlist in the Guard on a REP 63 Contract, which is their equivalent of an Army 18X Contract. That gets you 11B Infantry School, Airborne, a pre selection course and a shot at Selection. If you can't hack it, you go back to being a regular 11B. I'll post a website that has more information on it. I highly advise finding the closet to where I lived, it does not have to be in the same state, and contact them about your desire to join. They will give you the really scoop. Be aware that all of the 18 series training is Active Duty, so plan on being in training for a couple of years if you make selection.
https://nationalguard.com/special-forces-non-prior-service-applicants