[darkpuppet]

Time and air. Febreeze can help a bit. A good detailer will be able to help out as well (maybe flo has more ideas?)

But the more serious question is if he should even be buying the car.

Smoke has a terrible effect on the plastics and the glue that keeps things like the headliner attached... effectively ruining the interior. Personally, I wouldn't buy a car from a smoker unless it was a great deal.