with resetconfig, you're clearing the entire configuration, including identities, policies etc. You can erase all logging yourselft by accessing e.g. via FTP and delete all the file content. The statistics are reset via "
resetcounters". As last for the reporting database you can clear this by the commands on the CLI: "diagnostic -> reporting -> deletedb". This will destroy the current databases and start over new. At this point the unit should be back to "factory default".
Regarding "wiping the disks", erasing the harddrives is very harmful to the units as you cannot restore the operating system without returing the Appliance back to manufactoring. You should verify first with your contact that you can return the Appliances non-functional prior erasing the disks.