I had to cut three post in the xbox and one on the lid. I also had to remove the metal sheilding in the lid. I've got a couple pics with the post labled in the xbox. You will also have to cut you a "channel" into the dvd and hdd holders to run the power splitter cable through. Not to hard, I just used some wire snippers.
Neo: You don't have to do any soldering, you will have to trace 4 wires out of the yellow xdvd harness and either put them in an audio connector or cut and splice them. Using the audio connector may look neater, and you haven't cut your wires. Check out this thread at xboxhacker.net
if you haven't already.