1st off: Since it has a capacity of 8GB that tell us one thing, it is not a 3rd generation iPod touch.
2nd: From here we need to know whether or not it has volume buttons on the left side. If it does then it's a 2nd Generation iPod touch, if not: 1st Generation. Another way to tell is if it can play music without anything plugged into the speaker port, i.e. does sound come out of it other than alerts or clicky like sounds. If it can play music or let out gaming sounds through an internal speaker than again it is a 2nd Generation iPod touch. If it can't, 1st gen.
3rd: If by 3g you mean the wireless network capability ala cellular network, then that's a whole different story which no iPod touch has ever had.
Hope this helps.