The only way to backup and restore your current firmware is to install a custom recovery and back it up to your external sdcard ( there might be adb method but have absolutely no idea about the commands ) otherwise you'll have to flash back again. I don't know if the update will brick your phone or not because most of the time the OTA update is the one that causes the softbrick just like what happened to you the first time around where it ask you to use Kies. That's why I'm recommending that you use odin to flash a complete firmware just like the NC2 you downloaded but only after backing up your current firmware.
Hi Joe,
Now that you have convinced me to use custom recovery which i downloaded from the link that you provided, Could you kindly provide me the instructions too for backing up the current polish rom that I have. Just in case anything goes wrong.
Thanks,
Nikhil