The best way to handle that type of quest is to use tasks. You would create a task in your DB and can reference the task information in the wiki, which is quite good.
You could do it in quest scripts as well. It isn't that hard to do. You could just use EVENT_DEATH in your NPC scripts for that NPC ID (ie. 12345.pl) in the specified zone. You would then need to keep track of the total kills using quest globals, which you can read about in the quest wiki page at the bottom here:
http://www.eqemulator.net/wiki/wikka...=QuestTutorial