The tail light repair process for a Mustang GT involves the following steps:

Obtain the necessary tools: You will need a screwdriver, pliers, and possibly a socket set.

Locate the tail light assembly: Open the trunk and locate the tail light assembly on the vehicle's exterior.

Remove the damaged tail light cover: Use a screwdriver or pliers to remove the screws or clips holding the damaged tail light cover in place. Carefully pull the damaged cover away from the assembly.

Install the new tail light cover: Line up the new tail light cover with the assembly and secure it in place with the screws or clips.

Test the lights: Turn on the car and test the tail lights to ensure they are working properly.

Note: It is important to consult your Mustang GT's owner's manual for specific instructions and to make sure you have the right tools for the job.