Main AC vents not blowing at all. (Other blow cold still)

[dbrum]

My AC vents are not blowing and they say it's an A/C plenum chamber that is not functioning and needs to be replaced. They quoted $620 and that seemed a little outrageous.

Is this something I can do for less myself? Is this even the problem?

I live in Arizona, it's hot and miserable.

It's a 2005 Explorer EXT

 

[homebrewing]

I've got a 2009 Ranger and I don't know if the pieces and parts are the same but... My Ranger wouldn't blow like it should. The fan worked and you could get some cold air out if you had it on MAX AC but other than that it was real weak.
I ended up looking in behind the glove compartment and when MAX AC is selected it will open up a cabin intake to provide the HVAC some more cabin air to circulate. When looking into that hole I noticed the screen just before the blower fan was very clogged (80%) up with leaves dust and other debris. Getting a little tube extension to the shopvac sucked up all the blockage.
Now it blows much better and is much more quite.