If you don't plan on adding any further NMEA 2000
instrumwnts to your system (unless the Garmein stuff is really old it may be NMEA
2000 compliant) just get the Actinsea for SeatalkNg. But if you are like me with other instruments that are NMEA2000 compatible go ahead and setup a NMEA
2000 backbone and join it to the SeatalkNG by making an adapter to join the two systems. There is not one readily avaiable so get a Seatalk
Male connector and a NMEA 2000 female connector and hook them to the ends of the respective backbones. Now you have one fully compliant NMEA 2000 network and don't have to worry the stuff that connects is SeatalkNG or NMEA2000.
Thant's the way my combo Garmin/Raymarine network is setup. The "old" NMEA 0183 wiring
is still connected but most of the units have their 0183 data turned off except that which goes to the Actinsea.