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Run a backup using Desktop Manager to backup all the data on your device.
Follow these steps to backup 3rd party apps : http://www.blackberryforums.com/rim-...arty-apps.html
Or when you get the new device, and you still have the current device on hand, run the switch device wizard.
To remove all data from your device, go to Options > Security Options > General Settings > Menu Key > Wipe Handheld.