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check out the hack

secetion and read all the info is there! if you get 3.1.3 you can't! at least right now! and nobody knows what firmware will be on your phone till you open the box!
 
And once this is done it should be ok if iPhone needed to be serviced under Apple Care Protection?

How do I find out if I have 3.1.?

Marc

Yes, they will not know that it was ever jailbroken after a full restore.

Go to Settings > General > About > Version (although it does not matter what version you are to be able to un-jailbreak)
 
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