Ok thanks Johnny, I asked about the side door because I had to take the headliner out of my Astra J GTC last month and I faced the same kind of problem. I removed front and rear seat and absolutely all the trims to see if it could go out by the side door, and the only clean way was actually to remove the windshield, what I didn't do. The headliner went through the boot opening and eventually damaged the corners, even worse when putting it back because the new fabric kept the bending marks.
So, for the Omega, removing the seats is the "peace of mind solution" from my point of view, in order to keep the headliner in the best shape possible.
Let's sum up like this for the saloon :
- By the boot : fastest solution but high risk of permanent marks because of distortion.
- By the rear side door : takes more time as front seats need to be removed but ensure almost no distortion.
- By the windshield : needs specific tools and knowledge, high risk of windshield damage if non professional, cleanest solution as it's maybe the process on the production line.
Those headliners are a pain, regardless the type of car, looks like they designed them to stay inside the cabin forever
