Rivet

Check YouTube videos to confirm this process if needed.
First, be sure you get the rivet in case you need it. Mine was melted and that was not obvious at first glance. The cover was melted and sagging down and that couldn't be missed!
Use your fingernail to get under the rivet head and just pop it off. Twist the cover a little and it comes off, along with the fan. That was a surprise. Be gentle with the fan.
Put this fan inside the new cover, put the cover in place using the cover feet for alignment and put the rivet back to hold it in place.
The rivet comes with a socket to go on the inside of the cover. Remove the socket and put in into the chasis, install the cover, and pop the pin in place. Takes almost no time to do and sure looks better.