Now you can get to the evap core. It's inside this hole, and to the left. The second pic is looking up and to the left, from the floorboard.
You'll be able to reach back up in there and start pulling stuff out...I didn't get very much compared to some of the guys on the other forum, but there was still some trash/leaves/etc in there that I was able to get out with my hand. I also used a toothbrush to scrub the core and reach back into the farthest corners.
After that, some of the guys on FSC said they used a garden hose, or the low-pressure hose at a drive-through car wash, to spray off the core. If you do spray it with water, most of it should drain out the condensation drain, into the engine compartment and onto the ground. Just take it easy with the hose, or it will be too much water for the relatively small drain hole, and you'll end up with water all over the floor of your cab. They said to just keep rinsing until the water coming out turns clear. I decided not to use the hose, and I went with some foaming, self-rinsing condenser cleaner, which I got at Lowe's. I just sprayed it back in there as best I could, and let the foam do the rest.
After a few days, I have to say that while the volume of air coming out the vents seems to be the same, it is colder. So it helped some, and all it cost me was about five bucks for the can of cleaner (totally free if you use the garden hose) and it took me about an hour and a half, top to bottom. Hope this helps somebody else!