Apple iPhone 3G

So my dilema is this... I am moving to an area that is not in the 3G map according to ATT. My friend has the first Iphone but lives in a 3G area. My question is this... If I buy the first Iphone off him for 199 will the only feature I miss is the GPS? Also will I get to pay for the old data package or have to pay the extra 10 dollars. I want a 3G but if the only feature I am going to miss is GPS and I can pay less makes more sense to me to get the old one for less since there is going to be a firmware update... any thoughts???? 😕