Great Barrier Reff Dive Sugggestions

I anticipate diving the Great Barrier Reef Oct. 2, 3 and 4th of this year.

I have a suggestion from a friend that I use a live aboard, but it seems
from checking dive operator web sites, these trips (1 or 2 nights out, seem
to go to the same locations as the day trips.

Am I mistaken and are there any suggestions regarding my short dive
vacation.

Also, what would one expect to find in visibility, weather and sees that
time of the year.

Thanks!