Help with mouse input and output?

Alright I think I am close here for coming up with a solution. I have a few questions:

So now that I have a script that will basically emulate a USB mouse, where and how do I add the code where it autoclicks? Will the two codes interfere at all? Will this downgrade the performace of my mouse to make it harder to play? Like my mouse is set to 1000hz by defualt but I am fine playing on 500hz if I have too but I don't want to play on anything that is delayed noticably.

How do I take attach the PS/2 cable into the Arduino?

Thanks!