How should one kasher a stovetop if it was previously used for treif? The oven only goes till 550. Can one put the grates into the oven to kasher them? What about the rest of the stovetop: is boiling water poured on the rest acceptable? There also a stove top griddle which is a bigger burner that has a special pan with grooves. Can that go into the oven as well?
The grates requires libun kal, which can be achived by heating them on the fire, or by placing them in the oven and heating them so that paper touching them would burn (hard to say exactly, but 400 Fahrenheit would be enough). For the rest of the stovetop, you can use boiling water, preferably in combination with even melubenes, a heated brick or stone (or other substance) that is moved across the surface.
If food is not placed directly on the pan, it can go into the over as well.
Sources: Rema, Yoreh De’ah 92:8; Rema, Orach Chaim 451:4, and Mishnah Berurah 451:32.