Garmin helm station and maps

[blackc2004]

I just bought a new "used" Fountaine Pajot Isla 40 and have so many questions!

But one of the things is there's an GM8410 and a GM742. The station at the nav desk has Radar, etc but the one at the helm doesn't. The broker is just telling me that I need to "network" the helm plotter. But I have no idea where to even start on that. Anyone have suggestions on where to begin?

I also need to buy maps, I was going to get the Garmin Navionics+ (https://www.garmin.com/en-US/p/1181129/pn/010-D2179-20) Do I need to buy two, one for each chart plotter?

Also if anyone has suggestions on how to learn about the whole overall system, etc that would be super helpful!