Yes, the ENH710EXT antennas can be removed and replaced.
The ENH710EXT is an 802.11n dual-band 2X2:2 device. If, for example, you
want to replace the 5 GHz antennas, then you will need to replace them
with (2) identical 5GHz antennas or a 2X2 5GHz antenna with 2 connectors
like the SA5219. The same is true for the 2.4GHz antennas, except the
replacement will be (2) identical 2.4GHz antennas or a 2X2 2.4GHz antenna
with 2 connectors like the SA2216.