It is not a major job. You will need to undo the B pillar mount for safety belt (torx bolt!). To reach the bolt carefully pry the plastic cover with small flat screwdriver. That enables you to remove the top B pillar shroud. Also, take off the door rubber seal from the top. Start at bottom where they are joined and work your way up via A pillar! No need to take it completely down, as the B pillar section is held in place by the rear side trim cover.
Take down the A pillar shrouds (three clips, just pull, but be carefull not to break (any of) them.
Take off the sunvisors and the cabin lamp (just pull, starting from the windshield end IIRC). Unscrew the two cloth hangers at the back. By now the headlining should be coming down on its own.
Go to the trunk area. Take down the rubber seal which is (also) holding the headlining in place. Wiggle the headlining ends out of side trims and take it out through the rear opening (as that is the only possible way).
Have a browse through my thread, there might be a picture of two when I was doing the ICE installation...
It might sound complicated, but it is really easy and logical to take it out.