You can use the nav antenna provided with the Avin. It works just as well as the OE antenna as far as I could tell. I never hooked into the car's GPS, just left the Avin antenna plugged in behind the dash. Also did one installation of the antenna in the roof lining by the dome light and mic area. Both got good reception.

The WiFi antenna is so you can hotspot your phone to the unit or use a carrier provided hotspot so you have internet on your head unit. We use it all the time from our 5G phones to watch youtube, Google maps, Pandora, etc.

__________________
2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)