Zeeba!
So the most basic form of programming is Scripting - which you already do.
Scripting and triggering in Hammer/Sledge for Half-Life is already programming. Don't let anyone tell you it's not. So you already have experience with 'boolean logic' (1's and 0's... On or Off, True or False) Think of a trigger_once being a variable with a value of "False". Once the player walks into it, that variable becomes "True" and things happen; such as turning on a light, or opening a door, or firing a multi_manager.
Expanding on that, A multi_manager can be thought of as a function; Once fired, it triggers different events at specified times.
Multi_sources are boolean conditional statements; they evaluate any number of inputs and are 'false' until all the inputs are 'true' (or 'on' / 'triggered').
The hardest thing about jumping in (in my experience) is overcoming the syntax of a new language - it's even harder when you're learning new concepts like loops, logic, structures and variables.
Once you get a firm grasp on programming as an idea, it's much easier to learn a new language/syntax/whatever.
So If you want to make games with code, you probably want to jump straight into C++. It's one of the most common languages and it's prominent worldwide.
w3schools is good, but might I recommend a more game-orientated approach.
Check out
3DBuzz.Com's C++ intro course. It takes you through not only the C++ syntax, but the general Idea of coding.
Aside from that, why not head to your closest bookstore and drop a few dollars on C++ for dummies?
Regardless of where you go to learn, the road is tough. You'll be thrown into the barebones introductions and you'll learn to print things to console, declare and use basic variables, then you'll probably move onto basic loops and functions. It's all very boring stuff and it takes a while to learn but stick with it. There's nothing like a poorly-written SDK (cough - Half life - cough) to turn someone away from coding.
I code regularly in C, and have a few dozen hours of C++ experience. I'm always here to help.
Good luck!