http://forum.xda-developers.com/showthread.php?t=1704668
[Stock Official Firmwares] New Firmware ! P5110ZCDMB3 CHN 21-02-2013
Ok, here's a thread to return to full factory stock.
Simply find your country in the first post and follow directions (I think in second post).
You will need a pc and an easy to use program called Odin.
If you need a later firmware I can find that. This should take you back to the 4.0 system, as your tab came out of the box.
I can find 4.1 if you prefer.
Oh, backup your internal sd, as I think it calls for a factory reset which will make you loose your data. This is only because you are downgrading, when upgrading you won't loose any data so if you go up to 4.1 you won't have to wipe.