As for the key, yeah, If you can get it to the accessory position, (I did it with a little banging after a couple tries) It can be taken out easily.
The little pin ONLY goes down when the key is in the accessory position. Once out, I opened it up, then opened the little silver colored side panel. The springs took themselves out (lol) and I took the tumblers out. I put it back together, including that cotter pin, and put it back in.
Now, as I understand, the the anti theft system is not in the ignition lock cylinder, but in the area it fits into, so replacing the cylinder idoesn't change that (getting one set to your key will make things simpler, there are several threads here about that).
Even with no tumblers, though, I have to have my 'special' key to start the engine. Any key or screw driver or pretty much anything can turn the accessory power on, but the anti theft device will not let the car start the engine unless it senses the right key.
(an added odd thing, the key now can come out, even with the car started lol)
As for how permanent the fix is, That depends. It probably isn't great it the car is a lease, or if you want to resell it, but it does not effect the running of the car, It may be a little easier to steal(it the thief maybe knew how to disable the passive anti theft thing), but then again, a thief would have no way of knowing there were no tumblers, and the wheel lock and everything still works.
GZetech, rep-points, allready done ;) TY again!