Editing animated textures (contains Portal spoiler)

[Arctic Fox]

You might remember that near the end of Portal there's a Powerpoint-type presentation in a room that's off limits to you. You can see it from the outside of a window looking into the room.

Is there a way to edit or create those sorts of textures? I don't really know how to edit them, and I normally edit simple VTF files by using the Photoshop plugin to do the dirty work. I want to change those three frames for a mod I'm working on.

Thanks!

Edit:
Oh jeez. See, this is what I get for not reading the stickies, I just saw the tutorials there. I feel like such a moron...