"So all I have to do would be to remove the cotter pins and then I'd be able to pull the cranks arms off just like that? "

Well, that's the crux-- those things can be on real tight, esp. if they've sat awhile. Madpogue's advice will work; the only thing I'd add is to spray some oil down into the pin-- WD-40 type or better yet, PB blaster, and let it soak awhile before proceeding to hammer away. I've had cotter pins so stuck in I had to drill the little @#$% out with an electric drill.

I'd convert to cotterless, BTW.