I had a close look at the tumbler and collar when I replaced my tumbler in the 300TE some months ago. I played around with snapping the collar back in WITHOUT the tumbler, to see what holds what. The base of the collar gets secured into the ignition lock assembly, not the tumbler, and it holds the tumbler in. As Ferdman said, the true purpose of the collar is anti-theft to prevent someone from using a puller to pop the tumbler out.

If I were you, I would get a Dremel moto-tool with the carbide cutting wheel to cut off the rim of the collar. Remove the chromed ring and dash trim piece first of course to give you room to cut all around it, and as close to the side of the collar possible.

As I posted in another thread, if you can cut the rim off the collar, the tumbler will just come right out. Then use the wire tool to release the collar. Yes, you will have to buy a new collar, and no I do not know how much it costs.

Good luck.

Edit- the collar or black shroud is officially the "ignition lock cover" and costs $16 ordered from Peachparts.