You seem to be looking at this incident like it was the end of the world. It sounds like a sticking master, or slave cylinder, from the limited information you have posted. You will not be getting the engine or gearbox replaced, so don't worry about that. Worst case scenario would be having to have the full clutch replaced, but this would only involve the removal of the engine or gearbox, and as this would be by Mini trained technicians, its not going to affect the value of the car.