There are some good guides out there on how to open the Xbox 360. However I have read a few places that people are a bit scared about opening the case from fear of damaging their console.
This guide is supposed to be a really easy guide, with lots of pictures to show you how EASY it really is. You would really have to try to break your Xbox!
Please note - following this tutorial will break the warranty sticker (located under the facia) and therefore void your warranty with Microsoft.
A Torx screwdriver - sizes 9 & 10 (try ebay or hardware shop)
Something thin, strong and