What is an uncomplicated postpartum course? in other words, if a woman with an existing mental health issue became manic following the delivery of her baby, would that constitute as a complicated postpartum course?

Yes and no. The terms complicated post partum course in most common use is used to describe issues with the female reproductive system and how it heals. Of course a mental breakdown is a complication and can follow the birthing process but would usually be described in ways that separate it from the obstetrical healing process. Delivery just unmasked a problem that could have surfaced anyway.