I’m scared it will be really hard!
If you did well in pre-calculus, Calculus AB won’t be too hard to do well in. If you study, use external guides and such to study for the AP test, etc., you’ll do fine.
Calc AB is simply a few concepts: Limits, Derivatives, Integral. Thats it. Some, including me, say that Pre-Calc is way harder than Calculus because it is much more confusing and much more memorization. Study these 3 concepts I listed above and you will be more than prepared 
Also, it is slower pace than calculus in college, so if your major requires calculus, it may be less scary to start calculus in high school AB than take it at full speed in college.
The Calc AB exam might be the most predictable AP exam. We did lots of free responses from previous years in class and when I took the exam, all of the problems looked familiar. I pretty much predicted what would be on the exam based on past exams. The class itself isn’t too bad either. I would consider it one of the easier AP exams especially if you have done well in previous math classes.
I agree with @class0f2017 Calculus AB is definitely one of the easiest AP courses as long as you don’t have trouble with math. A lot of people take the course and fail because they do not understand the concepts well. The problems are basically the same over and over again, and I can definitely second the claim that the free response is predictable. After taking many free response practice exams, you will sometimes ask yourself, “have I done this already?”