What usually breaks is the plastic slider or sliding jaw. I've never done a front one, but I imagine it's similar to the rear. If you do it yourself, be aware that the regulator has a spring that's willing and able to pinch fingers. Also be careful that you support the opposite end of the pin when peening it. You can break the new slider if you support only the plastic. There might be something in the archives about what lube to use.

Sixto
91 300SE
81 300SD