Good to know that you are "getting back to school".
As for myself, i did my Bachelors Degree part-time at NUS (4years).
Used to have an average of 4 classes (6 to 9pm) each week.
Generally speaking, the first couple of weeks will be very hard,
esp if your colleagues or your manager ain't the understanding
type. After that, once you find your own rhythm and hone your
time-management, stress-management skills (feel free to add all
management skills here....) you should find it easier. The most
important thing is you need dedication and perseverance.
Btw, just out of curiosity, what exactly is the course that you are
planning to take?