SonicWall? How to Remove???

I want to remove a Sonic Wall. Just unplugging it only prevents access to the internet. I will replace it with a Linux-based firewall. Apparently one just doesn’t unplug sonicwall boxes — it leaves junk inside the servers someowhere.

T1–>Router–>SonicWall–>Switch

The question was asked before, but no one gave an answer. How does one completely remove a sonicwall firewall, in addition to just unplugging it. Sonicwall doesn’t provide an answer.