To get this done you need to:

1. Download firmware RC29 from Google
2. Rename downloaded file to update.zip and place it in the root of your MicroSD card
3. Unplug USB cord
4. Turn off G1.
5. Turn G1 back on holding Home+End keys until you see the G1 image pop up
6. From that icon, open keyboard and hit Alt+L
7. Hit Alt+S to begin update
8. Follow onscreen instructions and hit Home+Back to finish
9. G1 will reboot to flash the new firmware
10. Voila! RC29 Firmware is installed!