I have a few things on PDF that I intend on whacking up here, extra rules and articles released back in the day in a publication called Gang War, as well as the Necromuda Magazine. Not necessarily hard and fast rules, per se, but they can add a bit of extra flavor to the vanilla campaign.
But for now, you can get the rule book and other info you need to be able to play Necromunda here. While you are there, you may as well check out the model range (and some of the other specialist games) they have on offer.
Apart from ebay, there aren’t many places that sell scenery in Australia. You can find the original scenery you got in the original box set on eBay from time to time, but as these are cardboard, they could get damage easy (though are great scenery IMO). After a little bit of looking, I found The War Store on the web, they sell modular plastic terrain. This type of scenery is perfect for Necromunda as it is scaled in 28mm, and it allows you to take it apart and rebuild at your leisure, depending on what the scenario calls for.
There are also Necromunda discussion boards, one of which being Yakromunda. You can find heaps of tips here, from converting gangs to making scenery, you can even flaunt your gangs and are great resources for beginning players.
Now you have all the information you need at your fingertips, get out there and stomp some loudmouth juve for spilling your cup of Second Best…