Air struts from the dealer are going to be $900-$1,100. Refurbs from arnott are $300ish. Many people including myself have gone the arnott path.

As far as driving it. Are they completely bottomed out and collapsed? If so, I wouldn't really drive it. When they are completely collapsed you basically are driving a car with no suspension. This could be unsafe if you were driving it with no consideration that you don't have the same handling, braking as usual. If they are just sagging a little bit I would say it is ok to drive but not for long drives. It depends on how badly they are leaking. If they are leaking a lot driving the car is going to make the air compressor work over time and then you will start wearing the compressor out.