Well you can check your os in settings app Settings-General-About-Go down to version.(mine is 3.1.2 yours might be 3.1.3) For your UDID now you go to iTunes when your device is plugged in and click on the serial number text, it will switch to your UDID then you select Ctrl+ C to copy it and send to developers !
i reccomded iBetaTest.com to start off testing. Then you have experience so you can get into the awesome betas here Good luck!