Hey Mate,
Firstly, in that model, it is possible to replace the airport card. However, upgrading it would mean you would put a different type of airport card. Therefore either the plugs wouldn't fit, or the system would not recognise it. Remember, there are some parts that cannot be changed in a computer.
If you were planning on putting a different airport in, I am afraid it would not be compatible.
If I answered your question, please click the answered button. If not, feel free to reply and we can go from there.
Falcon16