Adding GW prophecies collectors edition CD key to my account

If i already own all three campaigns, and I wanted to add a guild wars prophecies collectors edition cd key would it let me?

I want to keep all my characters that I have now, and just have the divine aura on all of them.

Also would I get any more character slots?

yes you can add it
yes you get aura
no more slots

Yes u keep all ur characters u have now