Difficult to turn key in ignition lock cylinder. Key question too.

[Green Monster]

My ignition lock cylinder is worn. I have to push the key down to get it to turn the key once insterted. Took me months to figure this out. I used to do the wiggle wiggle wiggle everytime till it turned.

Does anyone else have this problem?

I have new keys that were given to me by the previous owner. While the keys appear to have nicer cuts on them, they do not work as well as my old worn key.

So, here is my question. If I replace the ignition lock cylinder, do I have to change out the door locks too if I want to use the same key for both the ignition and doors? Or do the doors and igition use different parts of the key?