Just thought I would update my post as no one really had the answer to my question. I did the gearbox oil change today on my 2016 Q7 4M on 80k miles. While it was messy and fiddly I did it on my drive without too many issues in 3 hours.
Anyone thinking of doing this here are some notes:
The gearbox is a ZF 8 Speed and you need to order the ZF kit which contains 7 Litres of oil, the sump tray (which contains the oil filter and magnets), fill plug and bolts. I ordered mine from Autodoc for £189 and it arrived in a few days.
You'll need some diagnostic equipment so you can read the gearbox oil temperature.
Lift car on ramps/axle stands so it remains level
Remove underbody shield
Undo fill plug (10mm Allen Key)
Remove Drain plug and drain oil
Support the rear of the geabox
Remove geabox rear support bracket
Remove pan cover screws
Lubricate new sealing ring
Clean the gearbox mating surface
Install new pan using cris cross method
Reinstall gearbox rear mount
Fill gearbox until oil flows back out
Start the engine
Maintain 2000rpm for 20 seconds to fill the torque converter
Change manually into reverse and hold for 10 seconds then into first and hold for 10 seconds
Check transmission fluid temperate is between 30c and 40c
Now top up fluid with engine running until it fluid runs out again
When fluid coming out is down to a few drops reinstall fill plug and tighten to 35Nm
Reinstall under body tray
I hope this helps someone.