You cant learn how to program overnight.. Coding isnt like that.. its takes months even years to learn. Even then if you did learn it youd have to learn the source code.. So i suggest finding someone rather then trying to learn it urself
There are several books that have been published on just about every programming language in existence, for all different skill levels.
There are also several books dedicated to the development of games (and therefore to a lesser extent, mods).
Below are some links to sections of books I found on Amazon.com:
I agree with InsaneFool, if you want to learn properly, use a book, so you can learn from the ground up. Don't make the same mistake as I did: run proudly into the SDK and think you know it all from the comments by Vavle, without actually bothering to learn C++ (which incidently the Source engine will almost definatly be in) first, lol, i never learnt from a book i learnt from trying things and seeing if i got an error, this means you will be continueously embaressed when Onions points out your inferior knowledge