Re: Rear Window / Wind Noise
It's a bonded screen, glued in with adhesive as Fantom said. If it's lifting with the air pressure of a closing door then it should push up from underneath (don't push from the bottom edge as it might slide off!) It's not an intermittent thing, it's either come unstuck or it hasn't. The glue sets hard when they are fitted and this will need cleaning off before re-bonding the screen in place.
There is no need to remove any trim first, especially as there should be no broken glass to clean up, you may want to put a sheet accross the parcel shelf to catch the bits of glue as they are cut away (or ask the fitter to do this).
Otherwise just remember the two heated rear window spades on the bottom edge. If the fitter does this you can check they are on properly from underneath in the boot by removing the upper carpet section and ferreting around like a contortionist.
Probably the most important thing, if you're still driving it like that, don't open a window!!! It will blow it out, and then you will need glass!!
Best of luck.