Hi brindleandblond,
If you have a printer USB that you use to could connect the printer to the MAC, you can establish a connection that way and then modify the settings in the HP Utility.
The alternate option is to connect an Ethernet cable, get the printer IP address, and launch the Embedded Web Server (EWS). In the EWS you can go to admin and re-enable the wireless there.
Hope this helps. If you need more detailed instructions post back and let me know if you connected an Ethernet or a USB cable.