If your unit is stock... it's fairly self explanatory once you see what is coming up from the main cabinet, and all pretty much just unplugs easily...
Unplug AC power (green, white, black) molex from Computer
Unplug AC power (green, white, black) molex from Monitor
Unplug speaker/power cable (3 pin and 2 pin molex connector)
Unplug 9 pin serial cable from computer (the one that goes into the cabinet)
Unplug 25 pin parallel cable from the computer
Unscrew ground strap (bottom left) and remove the connection from the inside of the cabinet
Remove mounting bolts (hex drive) and bushings that hold the box to the cabinet.