I've changed my Orc into a perfectly fine Night Elf using WinMPQ and a program named Batch Rename.EXE which i got of
www.download.com
What you do is:
* Open model.mpq in your WoW\Data folder
* Extract NightElfFemale.m2 onto your desktop. This is the character model file.
* Open texture.mpq in your WoW\Data folder
* Extract all the files named NightElf*.* and NightElfFemale*.* (Dont extract the male files unless you want to change the male characters as well as the females) unto the desktop. This is the texture files that are used to cover up the model file, and without these you'll look like a orc in a night elf's body instead of a normal night elf.
* Now run Batch Rename.EXE and replace the words NightElf with Orc in all the files you've extracted. *** BATCH RENAME.EXE FROM DOWNLOAD.COM CONTAINS A VIRUS: NOD32 WAS ABLE TO CLEAN IT ***
* Place the folder which your extracted and newly renamed files are in on the desktop, into the WoW folder (should be Character\Orc\Female\ or something similar to it)
* Log in.
You can replace pet models in the same way, my vulture pet for example looked very much like a blood elf female.
This is all client side (the changes are only visible to you) and you're not tecnically modifying files, only renaming them, so im not sure it even breaks the EULA to do this.
Edit: Screenshot included. I'm quitting WoW so i dont really care my characters name is showing here, and i never really used any cheats / hacks anyways.
http://img137.imageshack.us/img137/8057 ... 9574uh.jpg