Since I'm waiting to get some 7.1 disks, and I can't use my CC because I put a new drive in it, I decided to perform the 640x480 upgrade last night.
The whole procedure went splendid. Thanks for documenting this on your web, Stuart! I was amazed as to how easy it was to snap apart everything inside the CC like a snap-fit model. Fonts look a little small after the upgrade but the desktop is huge. I have some barrel distortion so I'm going to have to try replacing a cap (there's already a cap at CL26).
Some thoughts for the future:
Mark all the connectors with a marker before you unhook. Makes things easier.
Instead of cutting the trace to pin 25, or cutting the cable, which some folks have had trouble with, I simple desoldered the pin. You might consider this if you have decent soldering skills. Worked like a champ.
If you choose to use a Dremel to isolate pin 8 of the transformer, remember to go light. You can cut all the way through the board if you're not careful. Luckily I didn't cut all the way through mine. Guess I should be a dentist.
Before the upgrade I tried installing OS 8.0, it would not install, giving me a "system bus error, try disabling extensions." After I did the VGA mod, OS 8 had no problems. I rebooted several times to make sure. But of course OS 8 is a downgrade and I don't have enough RAM (requires 12) to install it anyway so I'm still looking for those 7.1 disks.
Note to self: next time you put a drive in, pull the analog board, much easier on the hands.