Concur on the coolant level indicator. If you feel ambitious, you could
always try cleaning any goop off the sensor end in the tank (the likely
cause), but pulling the plug will only disable another semi-useless idiot
light anyway - no great loss. If you decide to pull it, make sure you seal
the exposed electrical connections (dielectric grease will work fine) and
then secure the wire so that it won't foul with any moving parts.

As for the flashing issue: there was a no-cost GM recall on the flasher unit
a while back. It was actually for the 4-way flasher switch assembly, but
that unit handles all light flashing functions. I'm not sure if the '97s
were included (my '00 was), but it's worth checking out. It sounds like your
Dad was pretty meticulous with the maintenance, so this recall may have
already been done. If you can eliminate the flasher assembly as the cause,
try removing each exterior bulb, cleaning the connectors, applying a dab of
dielectric grease (we have a theme here!) and re-installing. My old Cavalier
had a similar issue and it turned out to be an intermittent bad connection
on a rear running light. Cleaning, greasing and re-installing all the bulbs
worked for me then and it might for you now. Check out the recall first -
it's free (or should be, don't get ripped off!).

W.