You need to enter the Garmin Mapsource system. As well as being able to upload maps to your unit, the software becomes a full charting system for your computer. If you connect a GPS to the PC via the serial port (very easy), the system can navigate too. Waypoints, routes etc. can be moved between PC and GPS, GPS and PC.
If the 188 is permanently attached to your boat, you can shift waypoints into a handheld, take it to your boat and download them Garmin to Garmin. And vise vera.
The Mapsource Europe CitySelect uses the same software and will add itself to the system so the PC then, also, becomes a mapping and routing system. I you have a laptop, it can be in your car and the mapping will take you wherever you wish to go. Anywhere in europe, that is.