I've got a couple - my ears mainly.
If you're planning to get anything in your ears that isn't your earlobes (your upper ear etc), don't let them use the gun to do it!!
If they hit anything (capillary in my case haha) it has to be taken out, and it takes forever to heal. I had a bad experience there!
Plus its essentially a blunt object being shoved through.. :S
Umm, one of my friends has her lip done, and I went with her when she did it. It was pretty cool to watch actually!
If you do decide to do it, take a friend with you that isn't funny around blood or anything - you don't want them fainting half way through!
If you look after it while its healing, the chances of it getting infected are pretty slim. The piercer should tell you how to clean it after they do it.
I'd recommend Hairhouse Warehouse - I think they have stores in QLD? I get all of mine done there.
As for the legal age.. In South Australia, you have to be 16 before you can get anything done without your paren't permission. In QLD, I'd assume its a similar law.. The best way to find out it to just go to a store and ask them..