Remove the regulator handle clip using a rag as shown.

Inner handle removal/installation
Regulator handle installationMazda 6 Service Manual: Outside Mirrors
WARNING
Be sure to look over your shoulder before changing lanes: Changing
lanes without taking into account the actual distance of the vehicle in the convex
mirror is dangerous. You could have a serious accident. What you see in the convex
mirror is closer than it appears.
Mirror type
Flat ...
Mazda 6 Service Manual: Front buckle removal/installation
1. Perform the following procedure for vehicles with seat belt warning.
(1) Disconnect the negative battery cable.
(2) Remove the front seat.
(3) Disconnect the buckle switch connector.
2. Perform the following procedure for vehicles without seat belt warning.
(1) Remove the console.
...