1) If you just want to get rid of the lock notification, you can use Xposed. The Wanam module can change the phone to "official".
2) Look in the Verizon Note 3 section on XDA. I know there's a thread on restoring the AT&T version to stock 4.3 - there may be one for the Verizon version as well.
At that point you may or may not want to run the phone connected to the network before you bring it in. If you do, it will almost immediately try to install 4.4.2 (which I wouldn't let near any of my phones). You'll almost certainly get back a 4.4.2 phone, though. (And there's no way to go back from the official 4.4.2 to 4.3.)