Not the best place to ask. If you'll be updating to 10.3 or 10.3.1 using an autoloader then yes, it'll delete all your data. So make sure to back up your phone before with BB link.
But if you use the "blitz" method with Sachesi, then nothing will be erased, but it would be a good idea to make a back up before so if anything goes wrong you'll be able to restore.
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