I want to give my ECU a SW-update with SDD.

As ECU seems to contain the most central parts of the car, I fear to kill my cat... flash of death.

Is it save to select "configure existing ecu" or is there any special action with VIN or the ID-Block necessary in advance ?

I have done that in the past
Just follow the instructions in SDD

Its also a very good idea to have a psu connected (13.4volts)
you don’t want the battery (sdd top right) dropping to yellow or red during the update, defiantly not red

Cheers
34by151