Starting vg dev, which language?
C++. Reasons: large collection of libraries, backward compatibility with C, widely used.
Achieving good skill level in C++ will take from 2 to 7 years.
Also, I am assuming he would need an application for GUI and graphical development for the game?
There are multiple gui libraries, one of them is Qt 4, supported by nokia. There are alternatives.
Obviously we need a menu, and some graphics (unless we're doing a text-based game to begin with).
Graphics: gimp, blender 3d. OR photoshop, 3dsmax/maya/zbrush.
Menu - you'll probably have to write menu designer for your game yourself.
Now, let's get reasonable. Game consists of:
1. Engine (programming skill)
2. Music (composition skill)
3. Art (artistic skill)
4. Sound (sound recording/processing)
5. Script/story/idea (creativity)
6. Levels, ingame mechanics (that's game design)
Achieving mastery in each area most likely will take years. And developing a game takes time. You should expect that writing your game will take at least months, and aquiring skills for that will take at least year (if you're genius, that is). If you have previous programming experience, you can learn everything you need (though hiring someone to do it for you will be much easier) and write your game, but that won't be easy. Making a mod for existing game will be also easier than writing everything from scratch. Or you could use already available engine.