I am currently in the process of doing this myself, I stripped down the car a couple of weeks ago, it's quite involved and you need to take out back seats, parcel shelf and door cards to remove the c columns.
The parts are all with a local headliner guy but to be honest he's taking much longer than originally agreed, unfortunately the job is proving harder than originally thought as some muppet
previously tried a repair and used contact adhesive which has reacted with the old foam backing and is now harder than yesterdays weetabix in a bowl.
He's struggled also getting a smooth finish on the c columns due to the complex shape.
We've come to a gentleman's agreement on the price and the timescale as I want a proper job but I am beginning to regret not using Vampedtrim as recommended above.