For that, your best best would probably be to use qglobals. They are discussed near the bottom of the quest wiki:
http://www.eqemulator.net/wiki/wikka...=QuestTutorial
You would just set a qglobal on the char when they do the turn in, and in the EVENT_SAY, you would check if they have that qglobal defined yet and if so, set it to skip the intro part.