I want to restore my Galaxy Tab 10.1 to Factory settings?
Provided you haven't rooted the device, a factory reset will reset the phone to the state it was in. Note that sometimes, some extra content that was added by the manufacturer (like some bundled music/images) later may be wiped.

Obviously, if you're bundling along the same SD card that you were using earlier, format it and also run it through shredder programs.

Ideally, don't part with the same SD card - either give the next owner a new card or avoid it altogether.