The odds of the vacuum pump failing in the hundred mile trip home are almost astronomical. If it is the old style vacuum pump of course it should be changed out but not just to get 100 miles home with the car.
Now checking out the rusty old car for safety for the drive home might be important. No suspension point mounts rusted through especially. Brakes not dragging from sitting around etc. A quick check of everything never hurts before a trip with an unknown car. Some people do not warn you of a dangerous situation existing. Sometimes they do not even know it exists themselves.