Try finding some decent 5x110mm wheels for the ABS models this side of $2000 except stockers. You're just lucky the Astra-F only has a 4x100 PCD.
Anyway, Z20LET are hard to come by and finding a front cut is also hard.
Go to the site above and there'll be people who've owned Astra-F before.
Phillips makes head units to with the MFD. Blaupunkt do make head units that is also compatible with the MFD.
www.carshine.com.au are a place to get body kits but expect to pay with both your kidneys, your next child and both your testicles. TCCA in Artarmon also have stuff for it but you only need to fork over one of your kidneys and maybe your right testicles.