There is a few posts here already about how to make a NPC / Edit so feel free to check out the link since it's very helpful:
Editing a NPC that is already in game will require you to have:
LilProHacker's Data.Sah tool
ZeroSignal's shay_data_edit_0-1b/c
Python
And Microsoft Excel or OpenOffice (to view)
Those are the tools you will need if you are planning to edit or create an NPC. You can also do it in HxD but that's just a pain in the ***, and you would need a Hex Converter such as SubnetOnline which works pretty good.
Credits go to the Ubers here ^^ the rest will explain itself.