Sorry for the delay in responding. I was assuming the forum would email me when people replied ;-(
Anyway, all the steering wheel controls work ie volume up/down, changing channel/track, and mode. I contacted the company via eBay and their technical support guy rang back and was very helpful. He said the front camera is NTSC so would need to be replaced if I wanted it to work with their unit, and even then, it would have to be through AV2, so no steering wheel integration.
The unit is great so far though - I've got the SU62. Lots of nice features, including SD card reader. Here's the link on eBay. It says for Holdens, but is working fine in my Estima.
http://www.ebay.com.au/itm/DVD-GPS-navigation-player-car-radio-stereo-for-Holden-Commodore-VY-VZ-Monaro-V2-/281249994804?hash=item417bce5834:g:-f0AAOSwuYVWm2Gd