The ethernet cable can between the 5400 and 3400 exactly as it does now. The 3400 will not be able to communicate on the SkyView network, however, it can receive information from SkyView avionics via ethernet through the 5400.

the 73101 GPS is a Garmin 18x. The AFS #73102 aka SV-GPS-250 can talk to the EFIS at a faster baud rate, which will help smooth out the synthetic vision and flight path marker displays.