copy update.zip to root sdcard/
turn off gYoung
press volume up + home + power, press until display on
gYoung turn on in recovery mode, if not repeat step 2 & 3
choose apply update from sd card, use volume button to choosing and home button to "ok".
select file update-unroot.zip earlier
if finished, will back to main menu, and then select reboot now
gYoung was unRooted (just test by terminal emulator (type-->> su ))