@Caterina sorry, I really just can't remember and there doesn't seem to be much info out there about this. All of my sims that have this interaction are also scientists, lol I guess I play a lot of handy, nerdy scientists! Next time I get a chance I'll make one of my scientists quit and see if the expert repair option is still available or not.
I
think the benefit of expert repair over instant repair is that expert repair doesn't use any upgrade parts up. I remember being pretty thrilled to discover this interaction but obviously not enough to take decent notes! *face palm*
@tjtemple can you remember what level of the career this kicks in?