On my 2001 chev 2500 the flat blade screwdriver is inserted and the handle raised to unclip the airbag stud.(not turned) Also don't overtighten the torq bolts holding the horn switch, the springs need to move enough to disengage or the horn stayes on.
First thing to do is unhook the battery before u mess with the airbag,another thing ive read is to let the truck set for about 15 minutes after unhooking the battery because it holds a charge somewhere for a short period of time,so the airbag can still go off in case the battery is dislodged in an accident.