"One thing we did see was the day before the trip when we were at
Grease
Monkey (place like a Jiffy Lube) and after oil change, transmission
flush
and fuel injector cleaning, the CHECK ENGINE light was lit (first time
ever). On the computer it read Cylinder 2 and 4 misfire (could be spark
plugs)"

This is probably no cause for concern. The fuel injector flush probably
caused the engine to richen up to the point that it failed to fire on
several cylinders, and the computer detected it as a misfire condition
and illuminated the light.

"Lately we've been having an intermittent starting problem; sometimes
it
starts right up, sometimes it doesn't. It started a few days before
Christmas 2004, and it doesn't seem to be related to being cold because
it
doesn't matter what temperature it is outside."

Having read the rest of your message, I am going to assume that when
the problem occurs you twist the key and the engine does not turn over.
More information is needed to adequately troubleshoot this problem. You
need to measure the voltage at the starter solenoid when the problem
occurs.

If you do not have voltage at the solenoid with the car in park/clutch
pedal in, key turned to START then the problem is probably NOT the
starter. More than likely you have an issue with either a clutch pedal
position switch, bad ignition switch, or a bad neutral position
switch(auto transmission).

If you have 12 volts at the solenoid, and you do not hear a click when
turning the ignition switch to start..bad starter solenoid. Replace the
starter.

If you have 12 volts and you hear a click when you turn the key to
start but nothing else happens, then you have a bad starter and/or
excessive resistance in the wire leading to the starter solenoid.
Temporarily jump the start terminal directly to the positive terminal
of the battery. If the starter runs then it's possible you have
excessive resistance in the lead going to the starter. I've seen this
happen when the dealerships cut the main start lead to put in a bypass
relay. This is so they can sell you that $500 "no-start alarm". If you
tell them you dont want it, they typically put the wire back together
with a crappy crimp connector. After a few years it corrodes
internally, develops resistance..and you get the dreaded
click/no-start. Fixing it requires the affected section of wire to be
cut out and a splice SOLDERED in place to prevent future trouble.

If the starter doesn't run with a 12 volt bypass direct to the start
terminal then I would replace the starter.

Good luck with it.

Chris