Would the CPU speed affect my Gaming?

What happened in my experience is that it would run a little slow and seem to skip. So I would suggest clearing some space on your computer before buying and installing the game. It also depends if it is in 3D.

It really depends. As others have said, you'll only know for sure by trying, as each game responds differently. Some even have a minimum system check during installation, and won't allow you to install the game on a system that doesn't meet the minimums. If you can get it running, there are a few things that might make it better. Reduce the game settings to the lowest setting possible. If it's an option during installation, choose the largest possible install (copy as much to the HD as possible). The less the CPU has to pull from the disk, the better. Maximize the amount of RAM you have. Maximize the amount of video RAM you have. If you don't want to get a new computer, buying more RAM and a new video card can compensate for a slower CPU speed.

It will probably run a bit slower than normal. Most games have a tolerance for slower speeds, And you could trying running it with the setting turned down.