As my Tab 2 10.1 absolutely refused to "turn off", but always re-booted instantly, I had to modify the Samsung Rep Mark's procedure a bit -- and got a scare in the process -- but all DID work! ...thanks to Broadbill for posting this "official Samsung method".
My modification:
at step 4, where it says (unplugged, according to svdriodguy's subsequent post) "UNplug tablet and SHUT DOWN THE SYSTEM" -- well, my system wouldn't shut down, as always, so I pushed-in and held volume-down and power buttons per step 5 before it started to automatically repower-up... and Viola! it did give a DOS-like text-screen, showing it's into the recovery process, with the step-by-step choices shown in steps 6 and 7.
Here's where it got a bit scary: the option which I was to select in step 8 did NOT show up! ...no "install.zip", but only "update.zip" -- so in faith, I selected THAT one, and (whew!) it did proceed to go thru a very slow install, with various text-lines of status showing up (I swore it was "hung-up" a few times, but nope, just takes forever... give it LOTS of time to update system and hidden files, etc...).
Then when I did the step 10 "reboot system now", it seemed to take forever to start up again -- and the displayed "battery" went thru a couple of graphical changes till it looked like it usually does... and then, I was back to my usual log-in screen.
Checking whether the device was finally up-to-date (from "About Device" screen, tap on "software update" then "update") and it says "the latest updates have already been installed".
AND: now using "power off" during shutdown, it actually STAYS "off" !!!!
success.
Hope these slight modifications, and reports of procedure-differences, helps others.
Wayne