You'll need to re-register with a new STB.
Open your browser and type in 172.16.30.84
This will open up the provisioning log on page, you'll need your PID number and password. Add the pc by giving it a name and then you'll get a screen saying congratulations !!!
Close everything down, unplug the STB for at least a minute, turn everything back on and you should be up and running.
The only thing to check with the tech is whether your new box needs a cross-over adaptor or not.
Good luck with this, if everything goes ok you should be back online within 5 minutes