First of all, you need to change navigation SW on your unit/SD card in order to use newest iGO maps. I'm a little confused as the unit from your link is loaded with Sygic app. Nevertheless if you want to use iGO maps, your first step is to install crack*ed iGO version on your unit/SD. As I'm not familiar with this particular brand, you need to provide some details about the current GPS configuration. The main question about the current configuration is/if:
1. navigation is installed on a SD card completely (software+maps)
2. navigation is installed on internal memory (software+maps)
3. navigation is installed on internal memory (software) and the map data is on a SD card
If your answer is 1 than, you have a good chance for a quick and simple solution. In any case you can provide some screens of your SD card folder structure as that's necessary for the next steps.