I can speak from personal experience that up until now, experimenting with the D3 was always playing with fire because there was no safety net to fall back on incase something went horribly, horribly wrong. Now, thanks to some great guys over at XDA there has been a flashable file released that has been proven to un-brick previously lost D3′s. Oh happy day.
The file can be found here. For instructions on how to flash via RSDLite, head on over to the thread over at XDA.