how do you remove the driver airbag?

I have a 1999 grand prix that needs a new driver side airbag. I removed the two screws on the back of the steering wheel, but it didn't come off. what else do i have to do?

nobody ever removed an airbag here? i just don't get it. the airbag on my 1996 monte came off easy after removing the two screws. is a 2000 grand prix that different?