The valve seals, particularly the exaust seals, are most likely passing
oil.  I'd be surprised if you didn't see some dried grayish oil
deposits on the old plugs.  It is a tricky job to do on the car due to
the recessed valve spring pocket design.  If you've never done *any*
on-car valve seal replacement job before, I wouldn't suggest starting
with this engine.

Hard starting like you describe could be a bad cold start time switch
or a plugged cold start injector nozzle.  Hook a DVOM to the cold start
injector harnass: positive to one wire and negative to the other.
(IOW, don't ground your meter on the chassis ground or the test is
worthless)  Count how many seconds that you get a battery voltage
reading while someone cranks the starter over.  Do this test at the
same temperature or time that the car typically fails to start.  They
usually have trouble around 70F-80F ambient on a cold soaked engine.
If you don't get bat voltage for atleast a few seconds then replace the
time switch.  If voltage is OK and lasts for a few second or longer,
pull out the cold start injector.  Leave the banjo pipe in place.  Put
the injector in something like a clear jar to catch the fuel spray.
Wait until the engine is cold again and crank the starter while
carefully observing the mist of gas coming from the injector tip.  A
fine mist is acceptable.  A dribble or no gas is not.  The injector
should operate for the "few seconds" I spoke of earlier, so be ready to
observe it immediately after cranking the starter.

Toyota MDT in MO