Planning on modding my case for the first time

Hey people!

I have a Thermaltake V9 black edition case <a href="http://www.thermaltakeusa.com/Product.aspx?C=1390&ID=1835">LINKY</a>

I wanted to cut a few holes in the motherboard tray so I could run my psu cables behind it. I've never done any sort of modding, so I'm looking for any tips or advice that all you veterans could give to a novice like myself, after all I can only cut once! I was going to start the cut with a drill hole then use my jigsaw to cut out the holes in a few places then sand down the rough edges so as to not cut up my hands or shear the wires.

In addition, I wanted to sleeve the cables to get everything nice and tidy. Looking on frozencpu's website, I see options for heatshrink and cable sleeving. What is the difference (if any) and what sizes should I be buying?

Also, as you can see I have a 23cm intake fan (GIANT!) on the side of my case with no filter. Any ideas on an easy fix to control the dust without decreasing the flow too much? I understand that there will need to be some sacrifice, I'm just trying to minimize it.

Thanks for your help!

Two words of advice. Tape off the squares or circles you want to cut and invest in some of the rubber gasket things that you can put on the edges to close the hole. That will help better then the sanding for the concern of your wires getting ripped up.