I'm trying to edit some vpk content as I want to edit a few .vpk custom player model addons for left 4 dead 2

only thing is, is that I have absolutely no idea how to access those files; one of them is a mod that changes the witch model in the left 4 dead 2 maps and the ported L4D 1-to-left 4 dead 2 maps like dead air and no mercy

if this thread is in the wrong section, please move it to the right onw, and I tried to look this up in the steam forums, and I couldn't find anything except a program called GCFscape and how it can extract vpk content, but I want to edit/mod/change the infected models

I'm planning on modding a few player/infected models to look more.......risky and probably quagmire worthy, hell, might mod an infected to look like quagmire (giggety), and change some weapons to look better (with backing up the necessary original files to prevent any crashings of course)

can anyone help me on this, as I want to use the models provided with the game as a base for my own creations, but I am willing to mod a few already created addons to..............compare my work