To get the felhunter you get the original quest from Carendin Halgar in the Warlocks Guild in UC. Here is a guide that I used to do it from the Warlocks Den http://www.wowmb.net/content/Undead-Felhunter-Quest.htm It gives you a step by step guide on how to complete the chain of quests. You should get it done in no time. Hope that helps. Good Luck
folsomdog