So, I got it to engage, and then went to get the Chilton manual. The manual didn't have anything useful in it, though, beyond a diagram of the latch. That's stuff I can see just by looking at it.
I took some hard looks. It's all gunked up from being in a car for 7 years but seems to be intact. All of the springs are missing, presumably from rusting and falling off, and that is the problem.
So, if I could find suitable replacement springs, and take the latch out and clean the thing, maybe that would do the job.
Where the hell would I fidn replacement springs other than buying a new latch?