Any line with a leading # should be treated as a comment and NOT TYPED. At the OpenBoot PROM prompt, enter:
Now you can reset the system (without disconnecting power!) and it will come up with the MAC address 8:0:20:XX:YY:ZZ.
Note: I couldn't find a clean way to set the NVRAM clock from the OBP prompt, meaning that on first boot, your OS will have a wacky time set.