Do I risk ruining my Aardvark device if I lose power during a firmware upgrade?

Definitely not. The Aardvark device firmware upgrade system is designed to check for errors. Even if the device is unplugged during an update, the Aardvark device will not be rendered permanently unusable. While the device will not be able to function in normal operating mode, it will remain in the special firmware upgrade mode so that you can try to re-flash the firmware again.