Would it be hard to gut the cat, or is it a task that needs professional work? Also, would I notice good gains and would there be any difference in sound?

It's very illegal, and very very annoying.

THAT IS ILLEGAL, DO NOT DO IT.

If you're just curious how to do it (wink-wink), take an air chisel with a long bit on it and go straight through the cat. I've also heard of people* who take a pipe and shove it through.

*= People may not exist, I saw nothing.

If thats what you want to do then done wreck expensive factory cats. go buy some high flow performance ones

i just cut mine all the way out and welded new pipe in and it made a big diffrence

Mine was cut open with a cutting torch and gutted and welded back in....sounds great!

99 Silverado and I cut out my cats, gutted them and then welded them back in. It was pretty easy and didnt cost me any cash. The truck sounded a little throatier but not much. Small increase in performance.

gutting the cats or cutting them out all together....wont that cause the check engine light to come on or any other problems with the computer?

If you have 02 sensors behind the cat, yes it will. YOu can get some simulators off of e-bay to plug in tricking the computer into thinking everythings fine.

mine didnt come on

Do you lose any low end power? I want to do this, but am afraid it will screw up low end torque, then I'm out 2 expensive cats.