Not feeling horny.
Not sure about the mk3. But I know for the mk2 you turn the steering wheel. Then you can see two small clips holding the airbag in. Get a flathead screwdriver stick it in the airbag will clip out then underneath is a torque bolt holding it in like a t35 iirc
Horns love getting stuck TBH, holding the button down while someone hits it (the horn that is) with something like a shoe sometimes works.