Hi Francis,
Price for doing the heater core sounds about right, I have had a couple of heater boxes out of GTV's and it is a MAJOR nightmare to do. Heater tap is relatively simple and cheap to do though.
If your wiper motor is faulty you can take it apart and inspect/ clean the connections inside the parking assembly- sometimes works and is cheaper than a whole motor. Where are you in Oz? I know of a few 2.0 GTV's being wrecked down in Melbourne if you need a secondhand wiper motor.
Clutch slave cylinder sounds about right and rear arm bushes aren't available separately. Usually it is the "rose joint" type bushes in the rear arms that become a bit creaky, again it may be possible to find a secondhand arm assembly- would have to check if 2.0 and 3.0 are the same though.
I would imagine there would be a lot of labour in fitting a whole rear bush kit- might pay to check before you order as getting the old bushes out would be a big job in itself.
