You press in on that pin and then you can take the assembly out and work on it on the bench.

If the ignition is locked up and that pin is frozen and wont push in, you must drill it out enough to get the assembly out of there. Iv'e never had to do that, and once was asked to do it for a lady - there is not enough money to get me to take that job.
So I always say: Fix this before it locks up, cause drilling the pin is just a PITA.

Since you had not chance to fix it first, you are stuck. So, get some nice new drill bits and get to drilling that pin, just enough that you can pull the entire assembly out of there. It's not as bad as I make it sound, but I"m 62 and cannot get in there and deal with it anymore.