Total newbie, ex iPhone user Q. re. 4.2 update

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http://androidforums.com – As title says, I've just moved to a Nexus i9250 after years with iPhones. Love the phone. I don't know anything about Android, so wanted to ask re. updating from 4.1.2, which was on the phone when I bought it, to 4.2. Oddly (or maybe not) I was getting a message every time I powered on the phone or woke it from sleep, that there was an Update to install. I always declined, as I didn't have time to sit down and do the update right. Suddenly, though, the message doesn't appear any more, though now I would like to update! Ain't it always the way? Under system info it says the phone is up to d (General)