Yes they will replace them, and no you do not need an appointment. Dock cables and earphones tend to just be replaced, no questions asked, in warranty or not. I walked into an Apple store with my girlfriend's earphones and nothing else (no receipt, no serial number for her iPhone, no appointment) and went up to the guy who takes Genius Bar reservations. I explained "these are my girlfriend's and they broke, is there anything you can do?" and he just called someone who brought me a brand new pair. I was in and out in about five minutes.