I've gotten into this thread too late
... so i'll jjst try and help with a few things that might have been missed. Gas in austrlia is LPG - Which is generally cheaper to run (for the time being atleast). Fuel prices may be up to $2/L by the time you get here, so LPG might even get to $1/L, just speculating.
Best places for free camping are known as State Forests. National parks are the next cheapest, usually around $5 a night. I can help with parks like these between Wollongong(~1.5hr south of syd) and problably just past Newcastle(~1.5hrs North of syd).
As far as sights around Sdney go, if your touring most of Australia, Sydney will be a low point
As will most of the areas between Newcastle and Wollongong. Theres really not much to see there that you wont see 10 times better in the tropics, bar the Blue Mountains. This (the Bluw Mtns) will probly be the higlight of Sydney, of course, not counting the touristy stuff like Hbr Bridge and Opera house etc. Check out Janolen caves, maybe the 3 sisters (overrated IMO), The Lost City in Lithgow is pretty sweet as far as scenery goes and whilst there you'd wanna see the Glow worm tunnel. (review/pics of area here viewtopic.php?t=255
- I'll have to get some more scenery pics next time
I use gas(propane) powered stoves, they and the fuel are readily available from all camping stores, and even place like K-Mart (usually have them cheaper there). Same with gas Lights however i havent seen one powered by disposable gas cylinders yet, so you'll need a BBQ cylinder, probly a 2kg would be good, nice and compact.
AS far as buying/selling your gear is concerned, try and buy car/campervan in a smaller town/city, or even on the outskirts of Melb/Syd/Bris, and then sell in/around the city. Prices are usually higher, and theres more buyers for a quick sell.