device: NUVI 670 NA:
software verion 4.90
audio version 2.20
GPS SW Version 3.00
Bluetooth SW version 0.00

This might be a simple question but I thought I would get clarification before i proceed.

I have downloaded the unlocked City Navigator North America NT 2015.20 (Canada/USA) map image and unpacked it. The packed content included one file only (GMAPPROM.IMG approx 2GB file)

Now I have the latest GMAPPROM.img file on my PC. From what I have read it should be just an easy copy onto the device (location: Garmin_Nuvi\Garmin) and overwriting the existing old GMAPPROM.IMG file......and I am done????? What about the other files (GMAPPROM.unl, gmapsupp.unl and others). Do they not need updating?

I find it hard to believe that it is that easy. However, before I do this I would like to back up the files on my device. Is backing up as simple as copying the device files (including hidden files) or do I have to make a disk image of the device?

Any help would be appreciated or point me in the right direction for IMG file installation.

Thanks