ignition cylinder ( thats what I have been calling it)

Ok fellas, I got a question.
On my 96 Z-24, I think my ignition cylinder ( thats what I have been calling it) is screwing up.
I turn the key and it will notstay in the lock postion when it's on, unless you turn it so perfect that it's barley hanging on by a thread or something.
but the slightest little bump will knock it back and shut the car off.
I almost got into a accident today when i went flying through a bumpy intersection and it popped back and the car shut off and the steering wheel lock up on me.
So my question to you is whats the part called that i need and do you think it would be a hard job to do.
Thanks for the help

its just the ignigtion switch. it is prolly not lining up with the inside metal piece or locking correctly... if you want you can try prying the plastic off with a screw driver or something else, if not go to a shop and have them replace it for you.... see the cool thing about that is, if you wanted to, you dont even need the key to start the car... if you do pop it off you could prolly use a screw driver or some other straight object to start the car, so when its off, take it for a test run, see if it still does that, then you know the problem lies furthur down in the ignition...