Well, when I took one apart the other day to fix the RROD, there was surprisingly little to it, besides a motherboard, ports, heat sinks and a single fan housing in the back for two fans. that's it. All I'd have to do is get a case, then make a support for the 360's board, to lift it up to proper height to allow the wires from the DVD drive to reach, then destroy a normal DVD drive, pull the tray out of its casing, then put the 360's drive in that casing, then make a flush faceplate for it, and let the drive sit in the housing like a normal PC. The lian Li thing I think looks ugly, and it's way too expensive for my tastes. Yes, it's already setup to accept all the hardware, but it's ugly. As for the other Xbox mods I saw on that page, I know that 50% of them can actually be bought online.
The problem is I want to also do this to the PS3, so I'd need to find 2 really good cases that are the same, that will accept both's hardware. The ps3 is way more complex inside and way better built, so it will take a larger case.