This morning, I used a clamp to squeeze the big metal disc inward, so I could remove the wire clamp:
The clip and disc removed:
And there was one o-ring. I am not sure if there should have been two, since there are two grooves:
Then I started on the front seal, first by removing the Woodruff Key:
But then I didn't know what to do. I'd read about taking out the innards of the pump, and how there are vanes that have to be kept in place or else they'll be really hard to put back in, but I was prepared and started trying to get the back of the impeller area out so I could push the shaft in and get access to the seal. It seemed that to get the shaft and impeller out, I needed to remove this hex nut:
But it wouldn't budge. I decided not to push it and decided to stop at my friends at Star Service in Tempe.
Meanwhile, I worked on the reservoir area. I just pulled out this clip carefully with pliers:
and removed the spring and stuff beneath it, down to the filter, which was interestingly just a ring of something between two metal plates:
I later took the pump to Star Service, and they took out the seal for me without having to remove the back end at all. Thanks! Now I will go and continue. More pictures on their way...