Even if you use RoHS solder paste, the flux is nasty stuff and it vaporizes. You can count on it getting everywhere the first time you use it. In short, once used for reflow, you must never again use it for food. And that means anyone who might come across it. Some day you will throw the oven away. You don't want someone to find it and try to repair it and put it back to use as a toaster.
So I liberally wrote on mine with a sharpie. The handwriting is bad, but hopefully the message is plain and will survive until the oven is reduced to scrap.
You'll notice that the original controls are still there. I just didn't bother to remove them, but they aren't connected to anything and don't work. The light doesn't light up anymore.
The low voltage wires just come out of one of the vents, but that's ok. The worst that could happen is that they short out and draw 30 mA of 5 volts or so.