you should first get information before starting to mess with your phone. when someone asks me to flash a phone i have never flashed before i first do my research so i know what can go wrong and what i have to do in case things go wrong! after collecting all the info ill see if it's worth the risk. if all people did that there would be less topics from people who f***** up their phone.
as for your gdfs, if you don't have a backup then you are screwed