You gotta take the whole instrument cluster out and then it's a twist off socket for all the lamps. You might want to either check with the Ford Parts Department for the exact type, or just take out the lamp first, and then just match it to one from the auto parts store.
I had to replace one of the illumination lamps and I think it was the same kind you would use for the side marker lights.... Like # 191 or something like that........
Taking the cluster out is not really that hard. It's best to have a shop manual to take you through the steps. There is a specific order that needs to be followed.
Hope you have not been riding around with the CEL on for a long time for it to have burned out!!