Came across this SMCC Sunsprint page a few days ago and thought I might suggest having a bit of a look at the Tasmanian and Victorian websites for some ideas and hints.
There are a few pdf help files there as well as plenty of photos of past cars. I have also just recently added a fair bit of info to the CHALLENGE HELP page on the Tas website.
Also be sure to check out the solarfreaks.com model solar challenge forum and feel free to post any questions you might like answered. Several national committee members as well as numerous past and present competitors are signed up to the site and so an answer should not be too far away.
While Jaycar is fine for things like car wiring and switches, places like Scorpio Technology, RI gear and solarmppt.com are probably more suitable suppliers in areas like solar panels, motors, wheels, gears, electronics, etc since many of their products are aimed specifically at the solar challenge.
Good luck with everything this year,