Usually, depending on country (your country's version of FCC also has to approve it before it can be passed to carriers for modification and approval), it could take anywhere from 1month to six, or it may never be approved at all by your carrier. Unbranded Samsungs get the update without all this BS.
In Kies on your PC (Note, Kies, not Kies Air. Also, on your PC, not Kies for Android), click on Tools>search for updates.
Yes you can update using unofficial firmware with ICS, like CM9, but you need to root and flash manually. Note that if you go through this method, you need to read a lot. A mistake in the process can turn your phone into an expensive paperweight. While the chances of doing so are slim and this is a worst case scenario.