Installing Cyanogen 5.0.4 onto my Nexus One

Here is my account on how I installed the latest Cyanogen ROM with the Google apps installed over the top. Anything you do to your phone as a result of following any of these instructions is completely your own responsibility, not mine!
After 2 months of owning a Nexus One  I decided it was time to try something other than the stock HTC/Google Android 2.1 that it was shipped with. I OEM unlocked and rooted my phone not long after it arrived. I just could not do without some of the conveniences I was used to like wifi tethering and speed!
A few things to note here before I get started on the detail. I did all of these things from a Linux installation and I had already OEM unlocked my phone and gained root access before. At the time of upgrade I was running Amon_RA recovery image and the MoDaCo version of the first OTA update.
To complete all of this, OEM unlock, install the Amon_RA recovery and subsequently install a custom ROM you will need to first grab the Android SDK which includes the "adb" command and a few others. You will also need to grab the "fastboot" command as well.
You can find good instructions on how to OEM unlock here and then installing the Amon_RA recovery image here.
Once you have performed both these operations the flashing of Cyanogen's ROM is a breeze.
I pretty much followed the instructions on the Cyanogen wiki page for install. Before you begin you will need to download the Cyanogen ROM and the Google AddOn ROM and copy them to the root directory (top level) of your Nexus One SD card. Once downloaded, the easiest way to get them there is via the Nexus USB connecting cable and drag'n'drop them there.
Disclaimer: Completing this install process will wipe your phone. This means you will lose all installed applications and settings, so I would suggest you find a good backup utility and back up anything that matters to you.
You will not lose anything from the SD card, so all your photos, videos, music and anything you have stored on there will be there when you are finished. I use "My Backup Pro" (the paid version) to back up all SMS messages, phone calls, home screen shortcuts and system settings. You can go without a backup and just install everything from scratch again, the choice is yours.

Flashing the Cyanogen ROM

The rest of the process is all done from your phone. So here goes.....

1. Boot into Fastboot mode on your phone.
   1. Power off.
   2. Hold down the trackball and press the power button at the same time. Do not let go of the trackball until you see the bootloader screen
2. Using the Vol/Up/Down button navigate down to the "Bootloader" option and press the Power Button on your phone to select.
3. You will see the Amon recovery bootloader now.
4. Navigate down to the "Backup/Restore" menu and take a nandroid backup. I cannot stress this strongly enough. Just do it - it could save your bacon!
5. Next step is to "Wipe" the phone. This is a must do step...weird things will happen if you do not do this. This is where all apps and settings get erased! This is the one and only warning!
6. Now select the "Flash zip from sdcard" menu option.
   1. Navigate to the Cyanogen ROM which you copied there previously and select it by pressing the trackball.  Confirm with a second trackball click.
7. Once this is complete navigate back to the "Flash zip from sdcard".
   1. This time select the Google Add on ROM with the trackball. Confirm with a second trackball click.
8. When this is finished, select the "Reboot system now" option.

All done! You will be presented with the original sign in steps to your Nexus One (you wiped it remember). Complete the process and be Wowed by the speed and extras features!
One cool option to enable is under the "Settings -> Sound and Display -> Display settings then find and select the "180 degree orientation". Spin your phone the full 360 and watch all the apps rotate with you!
Let me know what you think and if I have missed anything too :-)