Which part of the headliner? The part under the sunroof comes off easily.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

how does the part under the sun roof come off?

The fabric cover on the bottom of the sunroof comes out relatively easy (if you can get the push-pins undone without breaking them).

Open the roof 3/4 of the way.
Find 4 white pushpins under the front edge, there is a top pin (male) and a bottom pin (female). Each has a head like a large thumbtack.
Slide a putty knife or similar between the upper and lower heads of the pushpins, and pry them apart.

Open the roof all the way.
Pull the fabric cover out and up thru the sunroof opening.

Call the dealer and order new pushpins to replace the old ones that broke.

DG