In the oven?!? That seems a bit risky. We fixed several ps3s and xboxes a few years back. Basically just take it apart remove the CPU, hit parts with a heat gun, add new heat sync paste and put it back together.
Not a quick process. Every time I did it I spent at least 1 hour. The repair doesn’t last forever either. I think I got 6 months out of it before I had to do it again.