Where can I find any 25B positions that are open within the 82nd?

If you aren't qualified yet, then it probably won't happen, you can contact the Div, Retention NCO, tho any retention NCO should be able to look it up.

For what purpose? What would you do with the knowledge?

I would recommend requesting Ft. Bragg for your First Duty Station, if you haven't already chosen your top three duties stations yet. I'm currently in the same boat, I personally want Ft. Bragg as my next duty station. Unfortunately there's no real guarantee that you'll get exactly what you want, it really comes down to the needs of the Army.