I believe the FEBE add-on will package up FF customizations and port them to a new image.

Acronis software has various options for backing up Outlook data, Application settings, data, etc.

I'd suggest that if the data is "irreplaceable" that you re-think the "it's not practical" to backup/image the data. USB drives are cheap. As are DVD-R's.

I recently replaced my machine - I dumped everything to a USB drive, then plugged it in to the new machine. Most of the applications I downloaded the latest version and re-installed, but most of my data, settings, Outlook files, etc., came from the USB drive.

If you are using an ISP for email, as I was, set Outlook to leave messages on the server for some period of time until you are sure all of the data has moved over. Then be sure to turn that off before your server disk space quota fills.