Good question...

I got BWAauto to install it for me
While it's fairly straight forward, you have to take the nose off the car to install it - takes around 4 to 4.5 hours

You may need to re-gas the air con
The radiators are air con, intercooler, water

The Apr intercooler comes with larger input/output pipes

I also had the oil changed post the Marulan race day
Having upgraded to stage 2 I decided to change the oil every 10k (rather than every 15k)
(Using that German liquid molly oil)