Returning HTC M8 for replacement (via asurion), need to unroot, un s-off, and re lock

Hey everyone. I have an HTC M8 that has s-off, unlocked using HTCDev. Rooted by using "Sunshine S-off" application. Have also changed roms. I am having issues with the phone charging. I'm pretty sure the charger port is loose because its real touchy and charges very slow. Anyways, I have ordered a replacement / swap via asurion. I need to figure out how to get it back to 100% factory before sending it back. I have TWRP full system backups but only after the phone was rooted / s-off. I suppose I can find a download for the original stock rom somewhere. What is the easiest route for getting this back to stock?

Any advice an help is very appreciated!

-Charles