Interesting. If my mind and consciousness suddenly teleported into my body on september 10th, 2001, I would be in 6th grade and approximately 12-13 years old. I also would be with the rest of my class at a week-long beach camp on the southern shore of Taiwan. (I went to an American international school there).
When 9/11 actually did happen, our teachers decided not to tell us about it. There were also no TV's that me and the rest of the students had access to, and being in the 6th grade in 2001, not a lot of kids had cell phones. Instead, they told us (and i remember everyone being a little unnerved by the teachers' solemnesss) that "some of us might have heard about some things going on in the world right now, and right now there's a lot of confusion, etc etc". I shrugged it off and had fun for another day and a half without knowing.
So then come two days later on september 13 we finally got home and my mom asked me if i knew what happened, about the world trade center. I was like "What are the world trade centers?"
So to answer your original question I don't know. The teleporation experience would be so overwhelming that I think other things, such as going from age 20 to 13 again, surrounded by hormonal pubescent middle-schoolers would be a bigger issue.
I probably wouldn't do anything and possibly not even remember.
Even if it was possible to prevent the event from happening, I would have no way of reasonably knowing that nothing worse would come along later. The Taliban may develop a more catastrophic scenario later if delayed.