For a 15 dollar fee, you can change your character's gender, face, skin color, and "other cosmetic features determined by his or her race and gender combination." You are also able to change your character's hairstyle and color.
Character re-customization does not allow you to change your class or race, so you'll still be the same old Human paladin, just with a new appearance.
After you've paid for the service and been logged out for at least 30 minutes, a new button will appear when you log in that will allow you to begin the re-customization process. Simply click it and you're on your way to a brand new you.