The tracking information does not seem to update until or after delivery. My tracking only updated as arriving at the local post office the day before it was delivered.
My understanding is that 840p has a faster write speed than the 840. The difference is only slightly noticeable (maybe a second or two on boot times). There are quite a few resources easily available with a Google search of 840 vs 840 pro. Most people would recommend the Pro for the faster write...