I would change the fluid. This serves two purposes.
One you will know for sure its full.
Two its like the oil in your motor its supposed to be changed from time to time
BMW called it lifetime fluid to keep from changing it. Its not lifetime fluid its transmission fluid and should be changed ever 70k or so miles.
This isn't just about the fluid itself breaking down since there is a filter in there that needs changing and the clutches shed over time and can clog the filter and valves.