How do i replace the ignition switch on a opel rekord 1989 model;

On most cars.
remove the screws, in the plastic collar.. (look under there see em'?)
now its all exposed.
next, remove the security screws, from the ignition switch assy, clamp. (some are head less.) having fun yet?
then on some cars the assembly (IGN) will not come off with steering wheel inplace, its obvious at that moment..

the FSM book covers this, in vivid details. (factory service manual)