Will hold off on dist/rotor until next weekend -- cleaned it once two years ago and am probably due to replace it now.
I discovered that one of my spark plugs was apparently defective, and eventually failed, as the car really started to rumble a lose power after a while. I pulled each ignition wire to identify the non-working piston, and found it was number 5. To be sure, I swapped plugs with number 4, and when 4 would not fire, I knew the plug was bad.
The only replacement I could find at the time was an Autolite Platinum (copper core, platinum button tip) which should suffice until I visit my mechanic on Wednesday. So far there is no more significant shudder.
Now I am tackling the thermostat issue. I was able to find the housing and remove the hose -- shearing off the top of the lower left bolt in the process, but it can be salvaged. There is no obvious way to remove the thermostat, other than prying it out. Is that the way?