Nope. You have all the important points of converting a wireless router into a wireless access points. The only details left out are:
- Don't plug anything into the WAN port. It's not used.
- Connect the CAT6 cable beween the LAN ports of the two WRT54G boxes.
- You can use the same SSID to allow roaming. Success in switching between the upstairs and downstairs radios depends on how aggresively the client maintains the initial connection. Some clients (i.e. Intel Proset) are configurable making roaming easier.
- Since you're already run the cable between the two boxes, it's kinda late to suggest you try a WDS repeater. This will replace the cable and allow the routers to simultaneously act as a bridge and an access point. You'll need alternative firmware for your WRT54G boxes. I suggest DD-WRT at: formatting linkyou have a WRT54G v5 hardware, it cannot be upgraded with alternative firmware and WDS will not work.