Currently Being ModeratedMay 29, 2012 2:24 PM (in response to Bmw1409)
The Messages app comes with iOS 5. A 3G iPod can be updated to iOS 5. See:
However, many users have thought they had a 3G when they really had a 2G. A 2G can only go to iOS 4.2.1.
To identify your iPod:
The iPod touch (3rd generation) can be distinguished from iPod touch (2nd generation) by looking at the back of the device. In the text below the engraving, look for the model number. iPod touch (2nd generation) is model A1288, and iPod touch (3rd generation) is model A1318.