Seems a lot has changed since I bought back my car in 2003....
Getting an AP was very easy. Got mine in a day. As long as you have all the documents you should be fine. Same conditions like now, 9 months ownership, studying overseas for at least a year, etc. They'll also want to see your road tax and insurance overseas.
Customs was a headache though. At the time, my 1.8L Lancer was taxed at 170%!!! To compound the problem further, the customs will value the car THEMSELVES, not the value that you bought the car! They kept insisting using the Japanese price of a Lancer instead of the price of my Australian-assembled Lancer which was much cheaper. You can show your receipt, invoice, whatever, and they'll still ignore it and use their price.
Luckily though, the value of the car is negotiable. They'll consider depreciation, and of course deduct the value of the tax you paid overseas. I ended up paying about 90% of the value of the car for the customs duty, which is still quite high but better than paying 170%.....