Fill your boots.
If you don't already have one fitted into the device, you'll need an SD card in your Nav V. It's not necessary to fit one into the Nav VI as its larger internal memory can take the new maps.
Whilst you are at it, you might as well select the option to install the updated maps onto your Mac / PC, unless you want to rely on the software dragging the updated maps across from your device each time.
The whole process is painless (at least on a Mac) using Garmin express.
Old maps can be deleted quite safely from your home computer (at least on a Mac) using Garmin Map Manager.
If you don't already have one fitted into the device, you'll need an SD card in your Nav V. It's not necessary to fit one into the Nav VI as its larger internal memory can take the new maps.
Whilst you are at it, you might as well select the option to install the updated maps onto your Mac / PC, unless you want to rely on the software dragging the updated maps across from your device each time.
The whole process is painless (at least on a Mac) using Garmin express.
Old maps can be deleted quite safely from your home computer (at least on a Mac) using Garmin Map Manager.