GCFScape - Its an application that allows you to open VPK files! Whatever game uses VPK's , you can open them and surely edit everything you need or you want!

GCFScape can be find in thoes Pages :

Gamebanana.com - https://gamebanana.com/tools/26
Valve Developer Community - https://developer.valvesoftware.com/wiki/GCFScape

How do i open the VPK files?
When The application is downloaded , the vpk will have its own icon and when you duble click it , it will apear in a window full of folders , whatever is full of/whatever is even there!

Here is How you open the Main VPK file for L4D2's fiels
Steam > steamapps > common > Left 4 Dead 2 > left4dead2 > (scroll all the way down and find a VPK file called pak01_dir , You must open it with GCFscape)

And thats pretty much it... If i missed something. Please let me know in the coments!