Ignition Switch/Barrel
 

I have a voyager 2002 and recently it has been cutting out very suddenly. Had the cam sensor replaced but this has not solved the problem. The ignition barrel needs replaced because I can remove the key when the engine is running. Mechanic thinks that this could be the cause of the car cutting out. It could be causing a short in the ignition relay. I can buy second hand keys and barrel but don't know if that is going to cause problem with the immobilzer and is the ignition switch something that is built into the barrel. I have had all sorts of conflicting advice and just what to get my car back on the road.

Would appreciate any help