I made a detailed post in that thread about installing it; things that the instructions didn't cover, or didn't cover well enough--but short answer is no, you don't need to remove the headliner. The most you have to do involving the headliner is carefully pull the edge down about an inch so you can slip the wiring and connectors past it and tuck them away in the headliner. Everything else is simple as long as you follow the instructions closely and pay attention to the wiring colors specific to the Veloster.That mirror is sweet....I don't park it in a garage but the auto dimming and compass are worth it alone imo. Do you have to take the headliner off? Anyone have an install video?