Is there a way of telling if its a 1st gen?
Hi! I found this Wikipedia article:
http://en.wikipedia.org/wiki/Time_Capsule_%28Apple%29#Product_numbers
Look at the "Marketing model number" and the "Model number" rows -- one of those numbers should be on the box and/or the purchase receipt. Then you'll know which generation and how old the TC is.
If it's a 1st-gen, you'll want to check its serial number against this article (
http://www.macworld.com/article/1152634/timecapsule.html).
According to this article (
http://support.apple.com/kb/HT3546), the serial number is also on the original box.
What exactly is dual-band please? (im a bit of a newbie

)
I could be wrong on this stuff, but I think it's something like this:
Dual-band refers to the ability to use both the 2.4GHz and 5GHz radio bands. Older wireless devices (like laptops) are 802.11g and use only the 2.4GHz band. Newer devices (like your MacBook Pro) can use 802.11n, on either the 2.4GHz band or the 5GHz band. N is faster/better than G. If you use the 2.4GHz band to support both type of devices, the G devices will cause the N devices to operate at a slower bit rate (I think), so that's "bad" for your throughput.
For bands it's not so simple -- often the 2.4GHz band is crowded by other peoples' routers, so performance can be much better on the uncrowded 5GHz band. But, I've read that the lower band can actually be better about transmitting through walls and such. So, it all depends upon your location.
Anyway, all TCs support both bands, but the newer ones allow both bands to be used at the same time, while the 1st-gen TC can't do that. Why would you want this? The only reason I know of is you can use the lower band for older, slower 802.11g devices, and the higher frequency band for new, faster 802.11n devices at the same time. Then the G devices won't cause the N devices to operate slower (as they would if they shared the 2.4GHz band).
So, as far as I know, this feature is only relevant to you if you have other "G" WiFi devices you want to connect to the TC router.
Hope that makes some sense!