What makes changing a parking light on a Mazda 6 so challenging is that there is so little room to work in. It's a difficult area to get to and to do work in. The good news, however, is that it is perfectly possible for you to change the parking light in your Mazda 6 and the only cost to you will be a bit of your time and the cost of a replacement bulb.
Open the bonnet. Locate the back of the headlight assembly.
Locate the small plastic cover below the headlight assembly. This is a black somewhat oval-shaped cover with a tab at the top.
Push down on the tab and, at the same time, pull the cover toward the rear of the vehicle. You may want to use your slot screwdriver to help pull the cover off, but use restraint as the tab is plastic and can break.
Locate the parking light assembly which is in the upper right hand corner of the recess. You may wish to use needle-nosed pliers to carefully grab the assembly and wiggle it until it comes loose and then pull it toward you. Do not grab the wires to pull--grab the edge of the plastic assembly that the wires connect to.
Pull the light bulb straight out of the socket and push in the replacement bulb. Turn on your parking lights to see if the bulb works.
Replace the parking light assembly, pushing it back into place with your fingers. Replace the plastic cover, inserting the bottom edge of the cover first and then snapping the top back into place. Close the bonnet and you are done.
Some people like to disconnect the battery before working on the parking lights--if you choose to do this, remember to reconnect the battery in order to test your bulb before completing your reinstall.