what exactly do you have to do to remove and install a ignition barrel in a vp holden because i bought a new barrel from repco and want to use the old switch or put another switch on this barrel do i have to break the bolts and replace the housing for the barrel or can i just release the lock with a 3mm paper clip

Remove the whole assembly and a locksmith can swap over everything and cut the new key barell to suit your old key as well so the same key works on door locks/ign barrell. No more than $80 for it to be swapped over and barell recut.