Is going to an LED light just a matter of replacing the bulb inside the reflector unit or do you have to wire an entirely new lighting assembly into the niche and wiring conduit? My thinking here is that it should be similar to indoor household lighting with ceiling cans - you can just replace the bulb inside the can and not have to worry about the electrical wiring to the can.

Is it an easy bulb replacement or a more complicated re-wiring job?