[kh99]

What Ziki said - plus, I've always thought that it's very difficult to write mods without looking the existing code. There are some people that seem to manage it by guessing at hooks and variable names, but frankly that always amazes me. So I'd say if you want to create a mod the first thing would be to find the code responsible for the part you want to change, understand it (or at least the basics of it), then (hopefully) find hooks in places that let you modify it.

Edit: ...well, the first first thing would be to set up a test site on a local machine (using XAMPP maybe), and get an editor or something that lets you search for things across all the vb files (I use NetBeans, but that's probably overkill if you're not using it as a development environment). But I'm really far from being the local expert on mod development, so other people probably have some better suggestions.