I used to be really big on repairing 360's until I just got out of it recently. I didnt look at the guide meat provided but its more than likely the guide in which you remove the x-clamps which hold the heatsinks on the chip dyes and replacing then with bolts and washers which secure it better. This does work in most cases but is just a temporary fix.
The causes of the 3rlod comes from the GPU, the GPU uses BGA interface meaning that the chip is soldered using ball grid array underneath the chip and connects to the board. When overheating occurs the original x-clamps flex releasing pressure on the heatsink which in turn causes the chip desolder itself so to speak creating broken connections.
I have used the x-clamp removal method, along with using a heatgun and trying to reflow the GPU, memory, and southbridge and have had success with both, but let me remind you these are both just temporary fixes.
If you want a permanent solution you will want to have the GPU re-balled, but 360's are so damn cheap now I would buy a new one which do run alot cooler.