I don't think the over the air (OTA) mode is working right now because I did many tries and it keep saying device up to date so if you want to try it us KIES. if you version of KIES is not up to date you will have to update it first then you will be able to upgrade the phone.
it will take about 10 to 15 minutes of your time and it will depend on your connection.
everything like root will be gone after the update.
ok after you update, you will be able to go back and use the same method you use to to root the older version and install a different boot.
mine is working fine I don't find any problem yet.