Just to add, there will be a couple of wires to connect up that may well be specific to whatever head unit you have. The IS200 has an amplifier for the built-in roof aerial, and you need to supply power from the head unit to this otherwise your radio won't work (I assume this is the same on Australian models). There's a bit on this in the head unit removal guide, the aerial amp power wire is a black wire that runs alongside the actual aerial wire itself, this needs connecting to a suitable wire coming from the head unit, there's normally something handy that can be used for this, e.g. a wire that the head unit can use to power an external amp.
If you are installing a DVD player it might well have a safety device to try and stop you playing DVDs on the move, e.g. telling you to connect a particular wire to the handbrake wiring in the car so that it will only play DVDs while the handbrake is applied. If this is the case, then check the instructions for the head unit, but it probably just needs connecting to a suitable earth, and there are some bolts underneath the gearshift fascia that you can use for this.