1) There is a new firmware but if your Iphone is 1.0.2 DO NOT UPGRADE. Otherwise you can't unlock it yet. People are probably already working on hacking 1.1.1. There shouldn't be any 1.1.1 firmware phones on the market for another 2-3 weeks, guessing here.
2) There is supposedly a method to allow you to choose the firmware. Hold Shift and click restore for Windows and Alt and click restore for Mac. How true this is, I do not know but it seems to work. Oh this is if you got the phone but can't upgrade it to 1.0.2, this is NOT FOR DOWNGRADING. As far as I know, there is no way to downgrade yet.
switch to ATT if your worried, you lose your warranty, support, and support from your carrier if you try to unlock your phone and screw up. As for the version, just bought my 8gb a week ago and got a 1.0 version phone, so whatever you do, try to get it from a store and not online, as the online ones are sure to be newer versions than whats remaining in stock at apple stores.