Final answer:
The first action a technician should perform before opening a laptop case is to power off the laptop, and also unplug it from the power source and remove the battery.
Step-by-step explanation:
The FIRST action the technician should perform before opening the laptop case is to power off the laptop. This is important to prevent any potential damage to the system and to ensure the technician's safety during the replacement process.
Additionally, it is a good practice to unplug the laptop from the power source and remove the battery before opening the case. This will eliminate any risk of electric shock and ensure that the laptop is completely powered off.
By following these steps, the technician can safely proceed with replacing the hard drive without any potential mishaps.