The intermittent whirring and chirping from my GE Profile refrigerator condenser fan motor was resolved with a new fan motor install. The installation was straightforward and if not for all the other "plumbing" that gets in the way of removing the old fan motor and motor housing, this would have been a 15-20 minute job. As it was, it was closer to 30-40 minutes what with all the special hand manipulation needed to get screws lined up in a difficult to reach area.
After putting everything back together with the new motor, I have not noticed any fan whirring or chirping over the past 12 hours or so. Time will tell, as with most intermittent noises - but I am confident the new part will have solved my issue.