Top tips for flashing,
Run engine for couple of minutes, whilst it's running turn off heaters,radio and interior lights and remove any cig lighter chargers.
Turn off engine.
Connect a charger to the battery anything that will hold it over 12.5volts will be fine, not always needed but for the first timer always do this.
Do not touch anything or open any doors whilst it's flashing.
Its good to ecu ID everytime to ensure everything is working then you can flash.
Some times if it says remove fuse for dash, I don't personally bother I just ignition cycle and it works, this is my experience and knowing my tools. Up to you if you follow the same thing.
If it crashes, check your checksums and connections and try again but do not ID the ecu, just go straight to flash file. If it fails again then you need to take the ecu out remove the lid and boot mode flash it.
Remember these ecus are hard to break totally and can 99.9% be recovered.
Hope this guides you and takes some easy off your mind.