I changed it out, the housing had pretty much came apart on the driver's side. It is glued together plastic, so the gray goo that was on it must have been that glue.
I rounded off the back bolt that holds the housing to the block, so that was a major pain in the ass. I ended up pulling off the intake manifold so I could drill the bolt and got it out with an extractor bit.
When I first put the new thermostat housing in, I forgot to use the old o-ring (basically a black rubber band) so it leaked, that's when I rounded off that bolt.
When I installed the housing for the second time I used black high temp RTV at the block to make sure it wouldn't leak. I also used the RTV on the temperature sensor that goes into the top of the housing, because that was leaking as well. I probably should have just changed the o-ring out on the sensor, but I just wanted to get this done. (It was almost 100 degrees outside when I was doing all of this.)
So yeah, what a pain it was to change this part that really shouldn't have failed how it did.
Thanks for your help and take care!