There is also an extended FAQ, which we've posted after the break. This is something that we mostly never expected to happen, right up until Blizzard started saying that it would just a while ago. So at this point, once you roll a character, you're now able to (for an additional charge) change everything about it save for the actual class. It seems unlikely that Blizzard would ever let that happen (given that classes are the fundamental basis of a roleplaying game), but of course we've learned to never say never with them.
Update: We've now received official blue confirmation that it is intended to be active. Enjoy, everyone!
Gallery: Race Change Gallery