Hope these pictures help you. (Ignore comments on pictures, as I pulled this from another thread)
Remove all the plastic sections inside the box and look against the firewall side for the 4 Torx screws (part #7)......you'll notice these in one of the pictures below. These seem to be holding the fan unit shroud assembly. Undo these cautiously, as I believe they hold the ventilation cover (shroud) and the fan assembly located through the hole in the firewall, just behind it.
Also looks like there is a Water Outlet Valve (part #2) and a rubber stop buffer (part #3) located at the base of box that is press fit to hold the box down......just pull up on the whole box, to release it.
Goodluck!
