No, if you rename it it will not be picked up by the DashDAQ.

You should backup your Config File to the memory card after you change settings  through Set Gauge Properties. After all your Themes have been set up the way you want, and backed up, save the config file with your tunes and stock file. That way if something happens to your sd card, you will have a backup copy of the config file...

 To back up your config file follow these steps. From gauges, select "Exit". Next select "Setup", then "Memory Card". Then select "Backup". Now, select "Config FIle".