It would help to take the old switch with you ,but make sure you make a diagram and label the wires.The best Tech's always make a diagram.
Home Depot owns Hampton Bay Fans and they do have the replacement parts there.So take it with you.
I don't know if you have to just drop the Lamp asamble kit or the whole fan to get to the switch, but it should be easy enough to take out. Good Luck..Joe