97chevypickup

I have the truck named above. The ignition lock sticks when you try to turn the key. You have to wiggle it to get it to turn. So I bought a new cylinder, and I think I know how to change it, but my problem is that there is a warning on the instructions that says it may have to be reprogrammed. Does it have to be? What will happen if I change it and do not reprogram? Will the truck think I am an intruder and not start? And how do I have to reprogram it? Thanks guys!