You shouldn’t need to replace the entire roof lining in your car, but it will need to be removed to have the replacement foam and cloth covering applied. Any roof lining repair will involve getting rid of the old foam that has broken down and caused the delamination of the backing board and the cloth or vinyl. From there, the new foam and cloth can be applied to your original backing board and the assembly refitted to the car.
Another alternative is to have a new headliner installed, sometimes a reconditioned unit that some motor trimmers have on the shelf, ready to go. Some companies will even come to you and replace the roof lining in your driveway or work car-park. You can also source or buy a second-hand roof lining from a wrecked car which, in the case of a common model like a Holden VE Commodore shouldn’t be hard to find. You’ll still need to remove the old one and fit the new one, however. In some instances, you may still be able to buy a brand-new roof lining from the manufacturer, but that’s a long shot and will cost a lot more.
Meanwhile, a VE Commodore roof lining replacement cost will be roughly anywhere from $300 to $600 depending on whether you want the repairer to come to you, you’re happy with a standard (not custom) covering and the car is a standard model. A car with a sunroof fitted will add to that total as it’s a fiddlier job with more to remove and replace.
Repairing the roof lining yourself is not a simple job, as it requires the removal of a bunch of fittings such as interior lights, sun-visors, interior mirrors and that’s before you can even try to manoeuvre the single-piece roof lining out through one of the car’s doors. That’s the reason you see a lot of cars getting around with their roof lining patched up and held in place with everything from thumb tacks to staples.
This all goes back to the 1990s when car-makers discovered that a single-piece, structural-cardboard backing board covered in foam and then cloth or vinyl was a much cheaper alternative than the traditional metal-bow roof lining. The new system was also much faster to fit on an assembly line. But with time and heat cycles, the foam that many car-makers used breaks down into a fine, powdery dust at which point the adhesion between the layers is lost and the cloth sags down and billows into the cabin. Replacing the degraded foam and fitting new cloth or vinyl is the best solution and will return the roof lining to as-new.
There’s more information on what’s involved here.