Knappy,
Yes, there is a way to transfer the waypoints from your 997 unit to your new 998 unit. Just use an SD memory card to do so. Export the waypoints from the 997 unit and the 998 will load them when you install the memory card. Depending on what software version each unit has will determine where the menus for these are.
To export the waypoints with:
Older software: MENU>MENU>Nav menu tab> Export All Nav Data menu.
Newer software: MENU>MENU>Nav menu tab>Waypoints, Routes, Tracks menu>Options>Select All and…>Export.
Install the memory card into your 998 unit after it is running and it should ask you if you want to load the waypoints. If this does not work try installing the memory card before you start the 998 unit up (again this is due to which software version it has).
When you export the waypoints from a unit you are only making a copy of them. They are still in the 997 unit. So if you are selling that unit you may want to perform a Delete All Nav Data before parting with it.