Source Engine games
Source Engine games are relatively simple to rip, as a lot of public information about Valve's file formats are documented well.
You will need the following tools for source engine ripping:
gcfscape the most important tool. Allows extracting files from gcfs and vpks, which hold most source engine game data
vtfedit for reading texture files
For the rest of this tutorial I am going to assume you have extracted all of the files you need from the vpks/gcfs.
You just extract the .wavs and .mp3s from the archives. Pretty easy.
Texture ripping is extremely easy. Just open the .vtf files you wish to rip and just click export. VTFedit also has support for batch converting a whole folder
First off, you will need to rip the textures needed for the model.
Then you will need crowbar to rip models. Simply extract the entire folder the .mdl is in from the vpk/gcf and open the .mdl in crowbar's decompile function. (note: need to add detailed tutorial for this part)
Yes you can do this. Just open it in crafty and export it. Can give issues sometimes and occasionally won't load a texture or two, but those can be easily fixed by hand.
you will need gmad to extract gmod addons into files that the programs above can open. It is included in your gmod installation.