2003 Honda Odyssey how to remove the radio

I changed the battery and the radio now is asking for the anti-theft code.  I don't have it and neither does the dealer.  Apparently, my only option is to remove the radio and get the serial number.  Is there anywhere on line you know of where I can get instructions to do this.  The only other alternative is to pay the dealer $150.00 or more to do it for me.