Removing the switch is easy requires a bit of force, but you need to be careful not to tear the leather. The switch is held in with three spring clips, as you free them they expand and will catch the leather, so don't pull it out in a rush. Use plastic spudgers to protect the leather. If you use screwdrivers you'll damage the switch as well as it is relatively thin plastic.
Removing the selector knob just requires a firm tug. you then need to separate the rear section by removing the two rear screws.
Once the screws are out, you'll need to release two latches to separate the two halves. You can see the latch below, there is one on each side.
To release it you'll need a thin flat head screwdriver. This will be fiddly and require patience as you can only release one side at a time. Being rough will break the latch and junk your part.
Once you've separated the rear you can remove the selector cam and have all four parts laid out.
The issue that prevents selecting the parking light is caused by an injection moulding line inside the switch that makes the edge too steep for the cam to climb. It is very subtle, so I've highlighted the projected edge below.
You'll need to file off the excess with a die grinder till the movement is the same on both sides. You will be able to place the cam back into the housing and rotate it to test it before fully assembling the unit.
So if your parking light isn't working - that is how you fix it.