Minecraft mod crashed my game!?

I had just gotten back into the game, I installed a few mods, tried downloading sdk's gun mod (which required deleting lots 'o shizzle) did everything the guy in the video said (http://www.youtube.com/watch?v=_pHR3rM4WqM) and now it won't start, not even on the website (and no the download wasn't a virus I scanned it 5 times)