So in summary:
A CDR220 will work in Australia, but set the country setting to USA to get RDS (radio station name displayed)
If replacing a CDR21/210 with a CDR22/220, you will also need to remove the metal bracket.
To get the unit to slide in smoothly, remove the climate control unit so you can reach inside and sort the cables out
Installing an Ipod cable will mean you will disable the CD changer, which is not an issue in my books.