I'm very new to WoW modding and modding in general. I have a great interest in learning how to mod WoW, but I'm finding it difficult with my limite knowledge.

Right now, what I'd like to know is how to create my own custom display ids for my custom npcs. You know, new models, WoW-V let's you create new npcs but doesn't let you customize their appearance, all you can do is choose from a list of pre-created Blizzard models. I want to make my own models.

I'd like you to direct me to a tutorial that details in great detail, step-by-step, what I need to do create these custom models and put them in-game.

Thank you.  

EDIT: Just so we're clear here, I don't want to create new graphics or anything, everything I want my custom models to use is original content (no new skins, faces or gear), I just want to customize their appearance like you do when you're creating a new character.