I just did this for Mom's van. Yes, there is another screw on the backside. Fingers can barely reach it, but I could not get a wrench on it, even with articulated extensions. Just pull hard and break it off.
First, though, unscrew the duct actuator that is on the bottom and unplug the fan.
After that is out of the way and you tug and cuss to get the cover out, there is a duct door that pivots when the actuator you pulled off operates. You probably let it fall down when you took the cover off. This is a problem. Do not make it worse by trying to take this out. Just bend it over to clear the motor and impeller after you remove those screws. Again, swearing may be required.
Before putting in the new fan, you have to get the curved duct gate back into its socket. It has a finger on the top and fits into a socket. It moves smoothly when in the right place. Once there, hold it securely or you will just have to do it all over.
Bend it over while holding it up. Put the new fan in and fasten it. Keep holding that duct gate while you put the cover on. The bottom of the duct gate snaps into the cover. Get the cover tentatively fastened and check that the duct gate turns smoothly.
Tighten up. Add the actuator motor, plug in the fan connector, rehang that thin black wire and snap the glove box back in place. Put cold compresses on shoulder and hip to prevent bruising, because you have been working upside down in an awkward position.