I did this replacement on my '03 last fall. Though you could possibly remove the LED lamp without removing the spoiler, it doesn't make any sense not to. It literally takes about 5 min to remove the spoiler assy., and once you free it from the vehicle, you will see that the wire harness runs up from the hatch and through a hole in the drivers side post of the spoiler. When you pull the wire harness out of the spoiler, you will find a harness connector for the LED assy., inside. Just unplug it, then place the spoiler assy. on the trunk mat and remove the LED assy., just two screws. Install the new LED assy., pull the LED wire harness down to the drivers side spoiler post , pull it out of the hole and with the spoiler resting on the roof, reconnect the harness. Then reinstall the spoiler, and you are done. It takes less than 15 min total to accomplish the replacement.
As for those that want to try replacing the LED strip inside the high lamp fixture, you will have to cut the lens off the body of the lamp assy., because it is glue/welded closed. I know the new LED assy. isn't cheep, but look on ebay, to find a better deal on one. It is a lot easier to just swap the assy., instead of trying to repair the old one.
PS: This info pertains only to the factory spoiler. If you have one of the aftermarket ones, you are on your own.