If you have an Ethernet cable and a PC you should be able to connect to the devices LAN port and manually reset the wireless config.
The easiest thing is to go to Advanced Config at the top right and log into Luci. Goto Networking => Wireless and select the STAtion (Client) and “Remove”, then OK. Wireless should restart and you can then connect to the new STAtion, probably with out rebooting. Use the GLi GUI to connect to the new STAtion. Its much easier to use than Luci for this.
You may be able to just go to the GLi GUI and scan for a new STAtion, but I am not sure.
If you have customized your settings (IP, AP credentials, etc) you may want to make a backup of the settings and keep this on a USB drive. You can then reset the device and restore the settings. You probably want to leave the wireless STAtion unconfigured. If you installed packages, these will need to be reinstalled or some functions will not work.