The cheapest place for GoPros I've found is here: http://www.camerastore.com.au/
The video quality on their new ones is awesome, click the 1080p button in YouTube and you'll see what I mean. The audio quality isn't very good, but it's a huge improvement over their old ones. The 2nd camera looking into the car is an old GoPro Wide. They're pretty crap.
They have 2 buttons so they're easy to use, and the Motorsports Hero version comes with a heap of mounts including a suction cup. I was using a Ram roll bar mount combined with a GoPro tripod adaptor for the main camera, and a GoPro roll bar mount for the 2nd camera.
It's only happy laps, I wouldn't be worried about that. Come to a sprint day or something then go flat through the kink