I went home, got the thing undone, actually found the instructions that came with the faucet and got out the cartridge, which it seemed was the guy I wanted. But just in case, I bundled up the parts I had taken off and bagged them, brought them with me, along with the instruction sheet with its exploded views and part numbers.
Back to the Do-it Center. They did not have the cartridge, suggested I go across the street. I went to Quaglino's, they did not have the part either. But I noticed that these cartridges tend to be very expensive. That got me wondering if the cartridge was in fact the problem.
I headed for OSH with all my parts and instructions. When I finally got a plumbing person there he actually seemed to have a little more of a clue. They didn't have the cartridge either but he said the Price Pfister faucets are guaranteed not to leak for life so I should call the 800 number, probably Monday, and talk to a service person there, who should be able to determine what parts I actually need. And then they should ship them to me for free. That's what he said. We'll see if that is what happens. But in the meantime I am without a kitchen faucet and by extension a dishwasher, because I have to keep the water shut off under the sink. I can use the bathroom sink, though, just a little inconvenient, not a tragedy. It's not like I'm hosting a party or anything.
Almost every plumbing story I have to tell tends to get long, like this one. This one isn't over yet.