Help with switching mounts?

[Asilia]

Hey, I'm somewhat new to model editing, (somewhat meaning that I used to model edit back in BC) I quit WoW over a year ago and recently started playing again, and I'm wanting to get back into it, however things seem to have changed since then... :\.

I'm kind of a noob at trying these things out so I've come seeking help on how to change my mounts, for clarification, I already have the .mpq files of the mounts I want to switch(I had someone convert them for me), all that needs to be done is putting them in the files, but I don't know where to put them or what to name them. Also do I need to run wow through a 3rd party program (Like an MEFix like you used to in BC)? If so, What program?

Thanks in advance for anyone's help.