I don't know of a way to flash the stock recovery over TWRP. I would imagine somebody has figured it out. But I do know the OTA's are extremely sensitive and they check for more then just the stock recovery. Back when the ZVC/B update came out I hadn't even flashed a recovery yet, just rooted, and I unrooted and took it and it didn't work. So I'd copy all your belongings onto your computer, make a back up and copy it on your computer as well. TOT your phone. Update. Then come back later and put your files back onto your device and use Titanium backup to take your apps and data off of the backup you made.
Maybe somebody else know of a different way. But you can brick your phone taking an OTA with system modifications, and that will be a whole lot more work than rooting and flashing a recovery again.