Suggest that you do lots of research on sites like cruise critic which will tell you all you need to kno.
I traveled on the Galaxy a few years ago and it was my first time with Celebrity. The ship is very glitzy in comparison to other cruise ships, but not in an offensive way. We had such a good time we booked to go with Celebrity on our return and have enjoyed a number of cruises with them since. I understand Galaxy is due for a refit next year, so it would be worth checking when that will be. If you are visiting Turkey, I would recommend a trip to Ephesus if you are docking in Kusadasi. Kind regard.
This class of ship has been more reliable than the others and after the refit, which is well overdue according to some, she will be great. There are some very interesting ports of call in that area most of which can easily be done on your own or with some companions. My suggestion would be to look, as is mentioned at the "cruise-critic" site but also to spend some time looking at the tours offered by Celebrity, RCI, Princess, and the like and pick out the bits you like then make up your own tours with trains, taxis, or walking. That way you do it cheaper, you are not restricted by the slowest, and you don't have to stop at those monotonous "tourist shops" (if you don't want to).
Like I say ...Great ship, terrific cruise line, and a wonderful part of the world....Leanne Down.