In the end, the shop installed new Bosch 7998 spark plugs, and it starts
and runs fine now.  So, yeah, I could have done that myself, but at
least I got more comfortable digging around in the ignition.  And Now I
have a new coil, ignition wires, distributor cap and rotor, too.

The fellow at the shop felt the plugs were quite old, 40-50K miles.
According to my records, GoWesty installed NGK spark plugs in May, 2011,
at 145,277 miles.  The mileage right now is about 168,520.  So, only
23-24K miles.  I hadn't thought it was that long ago.

One of the things I learned: I need to be more proactive about replacing
ignition parts.  Just as I learned the hard way a few months ago that
the fuel lines in the engine compartment don't last more than a few years!

What else should I be replacing, and how often?

Another interesting item: I haven't bought a lot of stuff from GoWesty
recently, but I still get a lot of information from their web site.
Here's what GoWesty says about spark plugs: "Bosch has discontinued
production of their spark plug for the water-boxer engine; therefore, we
are now stocking this NGK product, and have found it be an excellent
replacement."

The mechanic here in St. Helena says he doesn't like NGK, and he didn't
have any trouble getting Bosch 7998 plugs.  Is GoWesty saying Bosch
discontinued a plug that was more appropriate for the waterboxer?

Again, thanks, all of you, for your advice.