I was going to post some pics of the steps involved during the mod chip install. However I loaned my digital camera to a mate Andy to take to Chile on his company trip to Concha Y Toro's vineyards so I haven't got any pics of the XBox's insides and dodgy looking solder work and that's probably a good thing :).
There's quite a good guide to installing the mod chip here
Anyhoo if you're going to undertake a mod that requires soldering a few things spring to mind:
1. Get a decent soldering iron and decent solder. The temperature of the gas fired thing I bought was difficult to control and there was a severe risk of lifting the delicate tracks on the XBox PCB. I'd recommend investing in a good temperature controlled professional soldering iron such as a Weller.
2. Practice your solder work on a scrap PCB, especially one that is multilayered and has the same fine trackwork as the XBox.
3. It turns out there are 8 PCB revisions ranging from v1.0 -> 1.6b. Mine was a v1.0 PCB and unfortunately holes for the LPC bus were filled with solder and that had to come out before fitting the pin header assembly. The LPC bus holes newer revisions of the motherboard are fortunately solder free.
4. If you have a v1.6 or v1.6b motherboard be sure that your soldering skills are really good because MS made some slight but significant modifications to the outputs on the LPC bus which means you have to patch the underside of the PCB with jumper wires to get the correct outputs. Some of the newer kits such as the Xecuter 3 CE include a PCB rebuild assembly that reduces the some of the pain. There's still a high risk of accidentally creating a solder bridge between one of the solder points and an adjacent tiny (< 1mm x 1mm in dimension) surface mount resistor and from bitter past experience these little buggers are a bitch to put back on if dislodged by accident when trying to clear the solder bridge. I have a 1.6 XBox as well (that's another story) and didn't even consider trying to fit the rebuild PCB simply because the iron and solder I had weren't of sufficient quality to do the job. I'd get a pro to do it for you.
5. If you have a v1.1 - v1.5 board then the installation should be plain sailing and the only difficult soldering task is soldering the D0 wire in the D0/LAN LED/HDD LED harness to a tiny wee solder point on the underside of the mainboard (v1.0 requires this too). A magnifying glass would've been handy for this task.
More later and how I thought I'd fluffed the install.