Become? You don't need to "sacrifice" a character to make a Hero character. As long as you have a Lv55 character, you can make one of each Hero class on a server. (The only Hero class soon to be available being Death Knight.)
Turns out instead of custom emotes, Death Knights get a voice modulator that makes them sound dead. The male gnome actually sounds creepy. High-pitched, female races sound like banshees.