Toyota Repair: hi ace ignition key, release pin, lock cylinder

Question
I jumped into my hi ace work van and tried to start it. The key wont go to ignition . It is as if it has frozen inside. The key wont turn at all. So i figure that i will replace the ignition set. I took of the steering covers and the cover beneath the instrument panel to access any bolts to undo, so i can replace the ignition key set up. I can see a saddle that goes around the steering column, but it looks as if during assembly that they bolt it all up then snap of the bolt heads, leaving only the thread left. I suppose this is a security thing, however can you please advise me on how i can remove these studs so i can replace the ignition key set up or what ever it is called. thank you for any help you can give me.  

Answer
The entire ignition lock does not need to be replaced, only the lock cylinder that the key goes into, in order to get the cylinder out the key has to be in the "ACC" position, then the release pin on the underside of the housing can be depressed to remove the cylinder, if this is not possible the cylinder has to be drilled out and removed, theother way is to replace the entire lock assembly in which case the breakaway bolts have to be drilled out to get it off the steering column.