Does it have a serial management port on the back? If so, first establish a connection using Hyperterminal or the like. Edit the configs then connect via an ethernet port and then upload the firmware via TFTP. Typically, you'll need to have a serial management session along with a ethernet connection to update SonicWall appliances.

Anyway, that's all I can suggest w/o a specific model #

**NOTE***
I must have posted at around the same time as the post above mine. I have to start typing faster!!