first the wheel airbag has no fixing screws, (you have probably undone the audio switches).To take the airbag off first disconnect the battery for min 10 minutes. Look for the two diagonal holes which sort of follow to the centre. push a long screwdriver in here till you feel resistance from a steel spring wire. Apply a little pressure on the airbag, then press the screwdriver in, it delatches the holding spring and the airbag will lift clear a little. repeat with the other side and the bag comes out. You will have to replace at minimum 1/.airbag, 2/. airbag harness inside the steering wheel (vauxhall dont sell it!), 3/.the drivers seat belt tensioner. Lastly youl need a vauxhall man with his Tech2 to reset the airbag module. (the module is under the centre console under the handbrake, it can be reset 5 times for a small fault or probaly once for a major fault - or it may have gone totally).
TheLion, November 2010