Here's the Root Toolkit that will give you a copy of Odin:
[Galaxy Note2 TOOLKIT V2.0 SPRINT] Drivers, Backup, Root, CWM, EFS, Flash to Stock - xda-developers
And this page has the original, factory MD5 you'll need to return to full stock:
Galaxy Note 2 Stock Firmwares | Galaxy Note 2 Root!
Just make sure you click the one that says "Sprint Galaxy Note 2 SPH-L900". Once you've got all the Samsung drivers installed (assuming you don't already) and you've got Odin fired up, follow these instructions:
NOTE: This will *ERASE* your phone. It will be like you just pulled it out of the box, so if you've got any pictures, music, etc *BACK THEM UP FIRST*.
1) Boot your phone into "Download" mode: Turn the phone off, then hold Volume Down + Home and press the Power button. You might get a warning about flashing custom software. Just press Volume Up to continue.
2) Launch Odin and connect your phone. If you haven't done this before (since you installed the Samsung drivers) you will have to wait a moment for the drivers to install, then Odin will show "Added".
3) Make sure only the "Reboot" and "F Reset Time" check boxes are checked. *Nothing* else.
4) Click the "PDA" button on the right and select the MD5 file you downloaded from the second link.
5) Click "Start" (just a bit below the PDA button) in Odin.
6) You should see a green progress bar on the top left box and, once it's complete, your phone will reboot.
7) You are now running the stock "out of the box" firmware.