Iphone 3gs restore/jailbreak help!?

well my friend gave me a white iphone 3gs , he took it to the apple store and they said the system was fried. it turns on and everything but all it does is go into recovery mode. im trying to jailbreak it but i dont know what version it is. and every time i try and restore it on itunes it wont finish downloading the update. if anyone can help id be very thankful.