Checking locally here, you need to have it installed by an enginer.
We just had a crab bar put in, and even that had to be put in by the enginer. It will also have to be a weight bearing seat, not just a basic one, so be careful buying one that isn't suitable, they wont put it and risk their license.
It then also has to be weight tested, and that is expensive.

Yep, there are tight age/size restrictions, and if you need to have a car seat, and with the new laws you will for quite some years to come, it needs to be a special seat that can take the load.
We were quoted over a $1000, just to TEST the result if we wanted anchor points in the 3rd row, and that was without a seat being installed. So we just got the crab bar put in.
You might find it cheaper and easier to put the extra cash into a different car then a dic-kie seat... but check locally first babe...