Headliner and stainless trim clips installation

You got it. There are little saw tooth like attach points for the headliner hidden beneath the gaskets. I did once see a headliner installed while gaskets remained in place but custom made tools were used. To drill the holes for the reveal molding clips is dang near impossible while gaskets in place too so...
Tips... cover those rear seat bottom anchors or they will eat your knees. Hubcaps and a heavy blanket works for me.
Loosely install the screws for visors, dome lamp, etc... so you can locate those holes through the new headliner.