Ehhh unpacker has a tutorial that comes with it. Its in your tools folder Then of course there should be a tut for it in the modding tutorials section too
Basically you use it to unpack specific files (you need to know the approx name of the file) and then you need to set up your installation to use modded files. Complicated for starters, but tutorials help greatly.

As for my mod, its in my signature, links to my own little ORG section. Stickies will walk you through every step of the process