Note: I actually took AP Biology through my school, so most of what I learned, I learned in an actual classroom environment.
I honestly don't think that it would be terribly difficult to self-study for AP Biology. Having said that, I had an amazing time in the class and I really enjoyed all of the labs that we did. If you enjoy science classes, I would certainly take the class, but if you're only in it for the credit, then you would be fine self-studying.
All you really need is the Barron's AP Biology review book. It's practically like the Bio Bible (I might be exaggerating a little bit... but it really is). You will learn just about everything you need to do (fairly) well on the test. I mean, there are always some detail questions that you won't be able to get just skimming/reading an AP review book.
If you really want to study and really want to learn, you should get the Campell Reece Biology Textbook. I'm sure your school will have one so you won't have to pay like $200 for it. There is everything you would ever need to know about Biology (at an AP level).
Another tip, if you are planning on self-studying, and even if you aren't: you should really have some Chemistry under your belt. I don't think I can stress enough how much Chemistry is on the AP Biology test. Without Chemistry, we wouldn't even be alive. So learn your Chemistry; I promise it will help you on the AP test.
Also, if you take AP Biology, you might as well take AP Environmental Science... A lot of the material overlaps and honestly, it wouldn't require much more work if you're already studying for AP Biology... Click on the Environmental link for more information on the test (which I highly recommend that you take)
Finally, for just a little bit of practice (because practice is very important), you should head to the Sparknotes AP Biology Test Center; if you take a practice test, it'll tell you everything you need to learn and review and tell you where on their website you can find it! It is amazing!