I have a 2011 Marin Kentfield with a threaded headset that I want to change to threadless. I'm aware that I would need a new fork, which I would like to upgrade anyways. I assume I'd also need a stem and headset as well. Is there anything else?

Is the work/labor to do this conversion easy as switching out the parts? or is there any special mechanical work that I would need to have professionally done?