Hi Rusty,
Yes, the unit does retain all your previous setting when a firmware update is done. It remembers all the alarm settings, times, and ranges. However, when you do the firmware update, always save a backup file (it will ask if you want to do a backup when you load the new firmware) just in case something goes wrong. That way if the absolute worse happens, the factory can also restore all the settings. It is really very easy to do a firmware update, and as a beta tester, I have probably done over 20 updates on my units with no problems.
Best Regards,
Mel Jordan