AP Comp Sci is not hard in the slightest. For me, it basically amounted to a study hall, with around two programs due a nine weeks, and there was rampant cheating.
Don't bother taking A if you have any programming experience at all -- A doesn't cover very much, just the basics of classes, loops, and conditionals. AB gets into dynamic data structures.
As for out of class time, it would require zero if you have a good work ethic. For me, most days consisted of lurking on AT and surfing the rest of the net instead of programing. Then, a couple days after the program was due, I'd take three hours and write it. My final grade was around 97%.
As for the AP test, it's challenging. It's weighted 50% multiple choice, and 50% "essay" or whatever you want to call it. The multiple choice questions are tough. You can find sample questions on the net if you look. Then, there's the essay part. There are four sections. Generally, you're given a function header and then you have to write a function a couple times in each part. They can also ask you to make the .h for a certain task, then write a function that does something with the functions you included in the header.
If you know anything about programming, skip Comp A. If not, it might make sense to take it, though I'd still recommend learning the basics of programming over the summer and then taking AB. That way, you can take your senior year off.
Good luck with it, and feel free to PM me more questions.
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