Do Apple wipe your devices when you send or take it in and get a replacement? Can the next person who gets it recover your texts, contacts etc.
^^^ This.Best thing, bring it in already restored to new.
Ive noticed a lot of people on ask here ask whether their replacement is a refurb or not and most people agree its a refurb. Ive read 1 or 2 threads which say refurb model numbers start with F instead of M but is this true?
http://theiphonewiki.com/wiki/Models
https://discussions.apple.com/thread/3650829?start=0&tstart=0
Purchased refurbs start with F. Service part refurbs have the same M model number.
Genius bar devices can be new or remanufactured - it's a mix - if they can refurb enough phones, they'll use them, if not, they'll supply new ones. The only way of telling is via the serial number. Apple's refurbs, however, have a new battery and outer casing.
With regard to the data - everything on the iPhone (since the 3GS) is encrypted. The first part of the restore process is simply deleting the encryption keys. No encryption keys = getting no data back.
But, if you don't, the Genius will probably ask you to backup and then delete all your data. At least that's what I was instructed to do when I got a replacement.
I read on another thread if it starts with 5K, it's a refurb.