How old is the furnace? If you still have the manual/installation instructions, there is an "exploded" view of the furnace that illustrates the location of the motor. We may have this page in our manual that we could scan & send to you as we have a mid 70's Suburban.
At least with the newer units, these motors seem to have a planned obsolescence of 10-12 years, as we've had to replace 2 in 2 different furnaces in the last 3 years. The motors are not serviceable.
From our experience, the furnace will continue to run with intermittent squeals. When the motor finally seizes, no more heat (which usually happens in the middle of the night!)