From the specialized tourist guide that is always with you, you will get all the necessary information about every interesting point of the places you visit, turning the journey into a life experience. You do not have to make any preparations before you start your trip, looking for the interesting places and information on how to visit them.
The tour desk that has organized the excursion has taken care of it and is probably able to do it more easily and faster than you would have done it yourself, as there is a long experience and cooperation between Greek offices and cultural sites. What you can definitely do is choose the office with the most experience at the destination you’ve already decided you are interested in. A simple search on the internet will give you all the information.