Hi Kent,
If you are near Hornsby try John Spano.(he is also literally about 400m down the road from AllZparts so drop in to see Warren whilst you are there)
http://www.yellowpages.com.au/nsw/hornsby/john-spano-body-works-13599779-listing.html
He is a one man shop and specialises in rust repair for very reasonable prices. I can't guarantee he can provide exactly what you need for your budget, but he will certainly be able to tell you a no nonsense quote on what is required to get things sorted.
I imagine if you were looking for the cheap yet effective technique he will reccomend patching up all visible rusty areas and then fishoiling/waxoyl everything within an inch of its life.
The 20k+ quote sounds like a more meticulous job which is obviously the better way of doing it. (most proper baremetal restos are multiple figures more than that though!)
I have to book my Z in for some bodywork this year as well, so will be interested to see other reccomendations in this thread.
Last I recall, he John wasn't great on the phone or internet and still a bit of a character in real life but much better to deal with face to face.
Best of luck.