What the job actually is
A starlight headliner means dropping the roof lining out of the car, laying hundreds of fibre-optic strands through it by hand, and feeding them back to a light engine hidden in the trim. Ambient lighting runs fibre or LED strips along the dash and door cards on the same principle.
The visible part is a few hours. The part that decides whether you are happy in two years is what happens behind the trim.
Where cheap installs go wrong
Headliners are fragile and they stain. A lining that has been forced out and back rarely sits flat again, and once it sags there is no fixing it without replacing it.
Then there is the wiring. Power tapped into whatever circuit was nearest, no fuse, connections twisted rather than terminated — that is how you get a flicker at idle, a rattle over speed bumps, or a fault that takes an auto-electrician a day to trace.
What a proper fit looks like
Trim removed with the right tools so the clips survive. Wiring loomed, fused and run off the ignition circuit so nothing draws when the car is asleep. Colours and brightness set with you sitting in the driver's seat at night, not chosen from a catalogue in daylight.
And everything reversible — if you sell the car, it should be possible to put it back to standard without a trace.
Questions to ask before you book
Will my headliner come out, and what happens if it marks? Is the wiring fused and where does it take power from? Can I change colours later, and how? What is covered if a strand fails in a year?
A fitter who does this often will have a straight answer to each.