How to fasten rear window trim

Strange but True my 1994 945-turbo which I just recently purchased came
without the two plastic trim strips for either side of the back tailgate
window.

I have obtained the pieces in question and am wondering if there is any
special technique to fastening these strips in place.

At present some of the holes are free while others appear to have what looks
like a rivet left in place. What was it that held these strips in place
originally? (somebody handed me the replacement strips, I didn't get to
remove them)

I was thinking of removing the rivet, placing in plastic grommets and then
using screws to secure the strips. (trying to avoid metal on metal)

Also should one place any goo in the channel of the plastic trim strip that
laps over the glass? If so what sort of goo? (one may have to replace glass
at some point, wouldn't want to fudge it to the point of unnecessary
aggravation)