Skinning tutorial?

Yep so I need to know if there’s a tutorial for skinning.
I need to edit, for example. rebels and combines, and make the new ones into independent NPC’s and Ragdolls.
So I don’t wish to overwrite anything.

I have done skins for GTA games so I know how to edit them, but I need to know how to get to edit them and make them into ragdolls and NPC’s.

I’m planning to make a gmod movie and I would like to create the main character myself.

I might be repeating myself, but I need to make sure you understand what I mean.
-I need to know how to get the textures out of the game and into photoshop
-I need to know how to save the new files and make them appear in the game without replacing anything.

Get GCFscape, it will allow you to extract the materials from the GCF files. Then get the photoshop VTF plugin. There are probably tutorials around somewhere