The phone automatically downloaded the OTA, and tried to install it. With TWRP, the update failed and my phone is working fine now.
I don't need the rooting anymore (was for teetering, but with new data plan it's now included). So I'm okay with losing the root and all.
Using SuperSU I deselected the rooting, and after reboot RootCheck tells me my phone is not rooted. I still have TWRP installed.
Now, I'm stock MF1/ 4.1.2. How do I install the 4.3 update and remove the TWRP recovery? I found in another thread the 4.3 Tar file. Do I simply use Odin on my PC and flash it on my phone? What about TWRP?