i have a 94 cavalier. when i turn the ignition to start the car, the car starts just fine, but as soon as i stop the clockwise rotation of the ignition assembly, it "springs" back to the off position and obviously stops the engine. with a new ignition switch solve my problem, or is it the housing that the key goes in to?

It is the ignition key cylinder that is bad.In short when you buy a brand New ignition key setup your replacing the entire component.This is the whole part and yes it will have New key's as it is a different keyed component.The very simple is remove the old and install the new and done!I could get more technical but the short answer is the ignition swtich itself is worn out.Yes you will have a different key to open(the doors) and start the car unless you have a lock smith key them alike prior to installing the new key switch cylinder.That is about it.Personally I would just get the new ignition switch and just make some duplicate copies of the keys and have 2 keys to save the cost over duplicating the door locks to match.Just my opinion.

how do you get the key cylinder out?

I might be mistaken, but I think the spring is in the actual switch which is on the left of the key cylinder. If so, you only need to change the electrical switch, not the key cylinder.