I believe that you will have to replace the ignition lock cylinder. The new lock cylinder will come with a new key. Most of the time to replace these lock cylinders you have to drill out the center of them with a large drill bit. I have the procedure for removing the old lock cylinder and installing the new one. This requires removing the steering wheel and air bag. Let me know if you need the procedures for this as well. I hope this helps. Thanks.
There might be a retaining pin that is holding it in place that you have to drill out. I am sorry but I don't have any pictures for this so I am trying to just remember from previous installations.
I know you have the other part already seperated and out of the column but by looking at this picture does it look like this is what is holding the sleeve in?