The Gaming Den

So, I'm interested in modding a game, but not sure where to start. Specifically I want to mod the old Bully game to be a different school with different characters and a customizable protagonist.

Where the hell do I start with that?

Probably here: http://bullymods.net/news.php

Customizable protagonist is almost definitely impossible. Making a new school is an enormous undertaking. Expect to take months to even know how big a job you're looking at.