Got the wireless repeater parts up and running. The default firmware on the routerstation doesn't have the ath9k driver that the R52nm cards need. That's ok, I was able to flash in the updated OpenWRT 'backfire' using the 10.03 candidate from the openwrt site (using the 'factory.bin image which I understand you have to use the first time).
Reasonably simple to flash it over, using the instructions and tftp. One odd thing that was a bit disconcerting was that the instructions in a few places say to wait until the RF led turns off after reboot (with dire instructions saying not to kill power while the flashed image is being unpacked, so wait until RF led turns off). Unfortunately the newer images seem to have RF led set to default on(?), so you really have no indication of when the new image has unpacked. I waited 12+ minutes. Another gotcha for me, but clear when really reading the documentation, was that the default openwrt images only listen on the LAN ports not the WAN port ... given that one is working with PoE on the board that's a bit odd, so you really need another cable for the first connection.
The wireless cards came right up and I was able to follow these instructions for creating a NAT link between radio0 (my directional connecting as a client) and radio1 (my omni working as an Access Point). I found things a little confusing but one is able to work with the existing wan and lan interfaces and dnsmasq is already setup in /etc/config/firewall on the wan interface, so it actually worked very easily.
iwlist scan | grep SSID shows a list of the networks that the radio in client mode can see (ie the directional antenna) and I was able to confirm by rotating the unit that the directional saw different networks in different directions (although saw nearby/high power ones regardless of direction, probably reflections).
The LUCI web interface is reasonably useful, even lets you control the little green RF led (but not the other LEDs, which is a bit odd, perhaps they are hardwired?). There are lots of entryies for the LEDs for the ath9k driver, but my cards don't have on-board LEDs so I think they are useless for me.
Next task is to get familiar with the GPIO code and hack something up to control a servo via the gpio pins. Hmmm, that means buying a servo :)