Keep it simple.
First make a full back-up of your internal storage
If you have more than 40mb free space left on your internal storage, just copy the countrymap to your internal storage. So you have 2 coutrymaps on your device.
If your device is still original you need to patch it before you can use downloaded maps. And you have to activate your new map.
Fastactivate does both.
tomtom-tools-f127/fastactivate-latest-update-2014-now-includes-version-updater-tool-t9359.htmlDownload Fastactivate
copy it to the root of your internal storage and start it up
Chose option 1, update meta.txt
than option 2, activate maps etc
and last option 3, patch navcore.