Easiest way to flash a DM7020/7025 is through web interface.
Code:
http://www.dream-multimedia-tv.de/en/flashing-browser
If your using the loop through and you 7020 is tuned to a channel on a TP the channel being watched by the loop through receiver will be affected, it wont be able to tune. Doubt that it will kill the tuner, you will just get a message saying unable to tune or something.
If the 7020 is in standby you should still get a signal to loop through receiver, but dont think you will if its fully powered down.