You may have a problem with the switch itself...
Every vehicle I ever serviced put full voltage to the motor at highest
speed.  (No resistor in place at full speed).  So, if the resistor was
the culprit, then it should at least work at the highest speed.  I agree
with the former poster that indicated you should drop the (blower) motor
and check it against 12v.  If it doesn't spin at full speed, then the
brushes indeed may be toast, not unusual at 200K miles.  You may be able
to futz around with them and get a few thousand more miles from them,
but the real solution is replace the blower motor.  Once you know hou
have a good blower motor, you should have high speed operation at switch
position 4, otherwise the switch may be a contributing issue.  Of
course, if the blower motor works when hooked up outside the car, and
not at all inside, it'w worth another check of the fuse(s) and/or
relay(s) to make sure they are OK
Relative to lower speeds, (once you have high speed operation at the
highest position), you may indeed have a problem with the resistors.
Once you can locate them, it's typically a minor issue to pull them out
and even a visual inspection should indicate whether they are OK or not....

Some vehicles (though in the minority) actually require a separate
ground connection for the lower speeds to work.  In those cases,
anything below the highest speed won't work unless the ground is in
place. It sounds odd, but there are some really strange wiring setups in
some cars... (Like the way the in-tank fuel pump uses the same ground as
the tail/brake lights on certain models of Chevy Vega, making for
"interesting" action if the ground wire gets damaged in a rear-end
collision, or the 70's Malibu that would allow the radio to work if you
put the (standard transmission) in reverse and stepped on the brake
pedal... another "common ground" issue).

All worth a little investigation....

--Rick