It’s not difficult to one year transfer; however, there is the catch of being able to get courses.
I was in your same shoes with about 15 units of AP, but you will find out that it is usually impossible to get any courses you want or need to transfer. I would recommend applying for 2-3 community colleges in the area, even if you do not take courses at them. I did not end up transferring in one year, but I am taking a semester off right now because of everything I did attempting the one year transfer.
With your case, it may be easier to get classes because you are going to a university, but it is still unlikely.
You may find out that you actually do not want to transfer halfway through, a lot of people end up enjoying the school they are at when all of the high school gossip fades.
Good Luck!!