Ok, I see what I did wrong. The cards on the sides weren't actually deep enough down. They need to go far enough -- I set them all the way down in the end -- not just to hear the click of the release at the top, but also at the bottom of the clip. Then the whole thing just lifted off... like buttah
After that, a 10 torx at each corner at the bottom of the hard drive carrier. Lift the carrier out, being careful not to damage or pull too much on the still attached wires. Remove the side phillips head screws at the side of the carrier. Carefully press down on the latches at the top of each connector -- one for power and the other the sata cable, to remove them. And then finally, unscrew the hard drive spring-lifter attached at the bottom of the drive using the phillips head again. Voila! The HD is successfully and easily removed.
Thanks to you all, I now have no idea why I was ever intimidated to do this. You guys are awesome
I might post pictures of my putting it back together if I have time tomorrow.