I'm going to need to change some plugs around and this may result in the HG612 being switched off and back on. Anything I should be aware of?
Just power down the HG612 and disconnect the patch lead connecting its xDSL port to the external line. Leave the HG612 powered down whilst all other modifications are taking place.
Once the modifications/adjustments are complete
and a half hour period has elapsed since you powered down the HG612, then reconnect the HG612 to the power. Once it has fully booted and stabilised, reconnect the patch lead to the external line.