personally, i was a bit disappointed with AP classes. i only took AP english, the rest of them i just took the test(my school allowed this). for the most part, they study the same stuff and use the same books as the normal classes, but are more in depth. i had an odd habit of reading the text books at the beginning of the year and then formed questions based on what i learned. the rest of the year was spent chatting the teacher up and reading more in depth books. AP classes at my school were far to congested with students asking questions for me to get any face time with the teacher, so i opted out of them and just took the test.
dont sweat it. if you have even the faintest interest in the topic of the class, you will probably excel without even trying. dont be like me though... i had a habit of doing my homework during the breaks between classes and then forgetting it in places. my teachers always wondered about how scatterbrained i was, they would see me do the homework before i left and then show up the next day without it.