Is there a messagebox class where I can just display a simple message box without a huge GUI library or any library upon program success or failure. (My script only does 1 thing).

Also, I only need it to run on Windows.

You can use the ctypes library, which comes installed with Python:

import ctypes
MessageBox = ctypes.windll.user32.MessageBoxW
MessageBox(None, 'Hello', 'Window title', 0)

Above code is for Python 3.x. For Python 2.x, use MessageBoxA instead of MessageBoxW as Python 2 uses non-unicode strings by default.