that's correct, u connect the jvc to the uni iso(you should get a jvc to uni iso harness in the box along with ur HU), iso to existing plug(buy from supercheap)
sorry it's been ages since i've done this, but i think it was either a mazda or ford laser harness.
i just had a look on the website and it may be a ford harness.
http://www.aerpro.com.au/list.php
look under harness and then pick your car.