[Warranty] How to backup before sending iPhone back to Apple for repair ?

hey guys. im sending in my unlocked jailbroken iphone in for repairs. is there anyway for me to "reset" it or "re-lock" it so that when i send it for repairs, it looks as if it just came out of the box?

also, before i want to "reset" the whole iphone, is there anyway to backup all my files and applications? and then when i receive my iphone back, i could just reload my files and applications, etc back in to my iphone?

and another thing, when i do "reset" my iphone, will they still find traces of me unlocking my iphone? and if so, will this void my warranty?

thanks in advance

if you want to put your phone back to OTB state you have several options:

if you are OTB BL 3.9:

use iliberty to reflash your baseband to the latest version and then restore with itunes to 1.1.4 that should leave your phone like OTB.

if you are OTB BL 4.6 then you can download bootneuter and relock you baseband, reflash your BL to 4.6 ( in case you downloaded it ) and after that restore to 1.1.4 using itunes.

regarding your backup questions: there a many different ways, some automatic, some manual i recomend you do a search on this and decide yourself.

i have bl 3.9

would it hurt if i restored with itunes to 1.1.4, then reflash my baseband to the latest version, then restore again to 1.1.4?
i just want to make sure nothing will go wrong.

Thread's renamed, please read my signature about the thread's title format, thanks.