Well, I cracked open an XBox 360 controller this weekend and installed a modchip for a neighbor. It was relatively easy. Nothing really to report. It was an 8 mode chip purchased off ebay for under 20 bux shipped. 6 wires. power, ground, led hookup (to see the blinks for what mode you are in), the mode button and the two triggers. A little soldering and it was firing on all cylinders. Rapidly.
Only thing was the placement of the chip and the mode button. i had to cut a little of the case in order for the controller board to fit back in (nothing was cut on outside of case, jut a little plastic on the inside) and then bend the masts of the mode button down but it seems to be working just fine. Took about 20 minutes.