Starting with game development

Hello there,

I'd like to start diving into game development. I already have experience with languages such as C, C#, Delphi, VB, Python, Java, but I mostly work on business apps, which is what I also do for a living. I have no experience in 3d modeling or any graphics part of games, really.

Some time ago I started looking for suitable game engines/SDKs for me to work with and start the game from "scratch" (apart from the engine part of course). I tried Unity, UDK and Esenthel but I realized that I should first try to do something smaller, eg. do a mod for a game, to get the feeling on how games work and the general flow of them.

So I started looking for games that are relatively easy to mod, have good SDKs and good tutorials/documentation. I stumbled upon Source SDK (Half Life 2).

Would Source SDK be a good place to start? How much freedom does Source SDK allow, can I only tinker a bit with the already done games (like only changing the models or weapon stats) or would I be able to make my own, small, Half-Life 2 -like game with my own mechanics and features in time?

Any general tips or your own recommendations on how to start?

Any reply is welcome,

Thanks