Twisted,
The insert is held down mechanically. There are "bolts" glued to the back of the insert that fit in holes in the hood and are then held down by nuts. You'll need to take the heat blanket off of the underside of the hood to get to the nuts to loosen them. Once you get the insert off you'll be able to see how the threaded rods are held on.
My insert was doing exactly what yours is doing now. I removed the insert and cleaned/scraped the left over glue off the back of the insert (making note of where the threaded rods where) then I used J.B. Weld to put the bolts back on. It's been a couple of years now and they seem to be holding up just fine.
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong, it usually turns out to be impossible to get at or repair."
-Douglas Adams, Mostly Harmless