So sorry you had to join the club. But very happy for you that you have Dr. Hansen. He is the BEST. Great bedside manner and a true expert guru about AN across the world. Nobody has more experience or better outcomes, so you're in great hands.
I actually asked him a question similar to yours and his answer was that it is very very unlikely that there would be major changes in the tumor in a month-long time Frame. I even doubt that they'll do another pre-op MRI just because, even if there is a change, it would be so small that they would just see it and adjust during the surgery.
Your nervousness is totally natural and expected. While recovery is hard, in some ways the run-up to surgery is harder.
I wish you all the best, and please let me know if you have any other questions, especially as they relate to your care at the University of Iowa.