Resetting Android Phone from CyanogenMod to Original When I bought my (pre-owned) Nexus One, it came with CyanogenMod.

I would like to change it back to Google's official 2.2 (or 2.3) Android.

What does this entail and how do I go about doing this in the safest possible way (e.g. with bricking it or any other side-effects)?
You'll need to download official firmware.  You can find it by searching "nexus one stock 2.x rom", and XDA might be better than Google.  I'd also look up how to use the Android SDK to flash it, probably using flashboot through ADB.  I have a Galaxy S which uses another tool, so I can't help with more detail without looking that up myself ;)