It was exceptionally easy for me to do. I left the car on the floor of my flat garage as you can reach everything you need to without lifting the car. Removed airbox, battery tray, then opened the filter. It is best to do this after the car has sat overnight to let the filter drain so you don't get a big mess. Took the filter out then went under the car and opened up the drain bolt. Let it all drain, then remove the snorkel and wait some more. Once thats all done I used
this fluid/filter kit and
this funnel to do the change. The end nozzle of the funnel fits directly into the filter port so you can fill it from the top very easily. I put in the full bottles then installed the new filter/airbox/battery and let the car idle for about 5 minutes while switching through park/reverse/drive/neutral etc. Using OBDeleven I monitored the transmission fluid temp and when it hit 35c-45c I removed the main drain plug WITH THE CAR RUNNING and let the excess drain till it was a light trickle. Once thats done close everything up and use OBDeleven to do a transmission recalibration (I just used one of the apps for 10 credits). Thats all there is to it. Took about the same time as an oil change and was just as easy.
Edit: If you use that funnel, pull out the mesh filter in the base of the funnel. This will allow the fluid to go in much faster. It only took around 2 minutes per bottle.
Edit 2: Total cost for me at the end was around 120 bucks vs the 350 a private shop quoted vs 750 the dealer quoted. Very glad I did it myself.