Here are a few videos I've gathered up to better help you figure out how to take your xbox 360 apart and fix the 3 red light error.

Too also clear up any questions you might have, the X clamp trick also works on the 1 red light error, no doubt about it, because it's related to the GPU processor.

The first video is showing you how to properly take apart your Xbox 360.

The Second video shows you how to replace the X clamp (X clamp fix)

Video 1: Taking Apart Your Xbox 360

Video 2: Repairing Your Xbox 360 (X Clamp Fix)