I actually just added some holes in my case to route cables for the first time ever, and I was wonderfully surprised how easy it was. My dad had everything I needed except for the grommet edging which is cheap. And you might want to think about extension cables unless your PSU has some long cables.
Here's what I used:
1 - A Drill
2 - A Bi-Metal Hole Saw ($15-20)
3 - Hand File ($10-15)
To smooth out sharp edges
4 - Grommet Edging ($1.50 per ft) http://tinyurl.com/y9oj4gb
Put it around the hole you cut in order to keep cables from being damaged by sharp edges