Santorini ~ Oia Transportation?



Okay all you seasoned do-it-yourselfers (is there such a word?)....We are interested in traveling on our own from Fira to Oia and back. What would you recommend we do to travel between these two towns? We would like to spend several hours in Oia and then head back to Fira. Is the bus regular? What should we expect the cost for a taxi? Is it difficult to find a taxi from Oia to Fira? What is the travel time between the two towns? We will be in Santorini for 13 hours on a Wednesday. How late will the shops stay open when there is a ship in port until 8 PM. Do you see any problems with this day of the week? Aloha.