In New Zealand, it is recommended that LED downlights be installed by a licensed electrician for safety reasons. However, replacing an existing LED downlight may not necessarily require the services of an electrician, as long as the installation process is straightforward and you have the necessary skills and tools to carry out the task safely.
If you are unsure about the complexity of the installation, or if you have any concerns about your ability to safely install the downlights, it is best to consult with a licensed electrician. They can assess the situation and provide guidance on the safest and most efficient way to replace the LED downlights. It is always better to err on the side of caution and prioritize safety when dealing with electrical installations.