EX7000 Wifi Range Extender - Antenna change for longer range

[Fern007]

I have a NETGEAR EX7000 Nighhawk Wifi Range Extender. It comes standard with 3 antennas (I think of 5dBi of gain).
Question:
1. Can I change all 3 antennas to a higher gain one? 11dBi?  Where can I buy them?
2. Could I change "only one antenna" for a directional panel antenna which I will point to the router source direction? and keep the other 2 antennas standard.

Any suggestions are welcome...objective is increase signal level "reception" from router from clubhouse which it is 500 feet away.

[DarrenM]

Netgear does not support the use of Third party antennas use at your own risk.

DarrenM