this usually means that the lights behind your cluster panel has been busted. you can get these bulbs for less between $3-5 from your dealer. the odometer uses 1.5 bulbs - the one with a brown socket.
you can change it by removing the cluster panel. but before you can do that, you will have to disonnect the battery (take note of your stock stereo's security code, it will ask for it once you connect the batteries and it would not function without said code), disengage the driver side airbag, remove the airbag (this requires extreme caution since it can go off and may cause injury) and put it inside your trunk with the padded side up, taking off the steering wheel, then the cluster.
wish i could post a DIY on it sometime.