I'm not sure how similar the ignitions are b/t the T/A and GTP, but maybe this will help you. The source of the problem I was having is a small solenoid (
B) attached to the ignition module. When the key is turned off, it is
supposed to automatically move the pin (
A) out of the key cylinder and allow the key to be removed. In the event of a malfunction, there is a manual override (
C). However in my case there was no button attached to the manual overide, so you had to take the steering column cover off to get to it.
I suggest you try replacing your ignition key cylinder first. I got a new one for my GTP for $16 at AutoZone. Rather than replacing the broken solenoid or using the manual override button, I just removed the son-of-a-bitch completely. The only downside to this is that the key can now be removed from the ignition without the transmission being in park.