Class

I recently started playing and haven't heard anything about Light or Darkness yet... I understand that later I'll need to complete a quest to check compatibility with Light/Darkness. My question is: can I choose a profession for my Monk (for example) that is offered to me without any Light/Darkness requirement, like "Enlightened," and then later upgrade him to Ninja? Or is the Light quest required for that? P.S. The same question applies to the Knight... can I upgrade him to Crusader so that I can later make him a Dark Knight?