Did you mean Sprint Note 4 NK2?
No need to un-root but I'd recommend backup, factory reset and data format. Wipe everything but extSdCard and power down prior to starting dismiss mode.
It's your choice whether or not to burn the bridge or not. Flashing the OTA OG5 stock tar will prevent your bootloader from downgrading back to any older one. That basically breaks Odin downgrade.
If choosing to retain Odin downgrade capability, look below for link to a tar ball by tx_dbs_tx for OB7 to OG5 to get to OG5 from OB7, keeping the OB7 bootloader but runs with OG5 system regarding the ROM. I think you have flash OB7 stock tar first.
http://xdaforums.com/showpost.php?p=62274955&postcount=1
OB7 tar
http://xdaforums.com/showpost.php?p=56853325&postcount=1
Latest Odin
http://xdaforums.com/showpost.php?p=51767811&postcount=1
Here's a post that may answer any root issues with OG5
http://xdaforums.com/showpost.php?p=62241991&postcount=56
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