hot.  I know it's been getting hot but not to the point of boiling over.   I
have been reading in the Haynes manual but still am confused.  What should I
be looking for?  The book made reference to changing the temp. sensor or
something  to that effect.  What should I do?

What do you mean by it doesn't work?  Does it always read all way at the
bottom?  Does it move at all?  If coolant is boiling over from your
reservoir then you may have a clogged radiator or blown head gasket.  You
may also have a bad thermostat.  Is your water pump squeaking or dripping
coolant?

I think we need a little more info here.  If you think it's overheating it
would probably not be a good idea to drive it until you determine what the
problem is and fix it.