Google "Berlin Tours" and check out the website for "Original Berlin Walks" and "New Berlin Tours". Both are excellent. We used a private guide from "New Berlin Tours" during a recent visit who was superb.
You can e-mail both to see if they would provide transportation from the ship to Berlin. Bus, train, or car service arranged through Regent might also work out well. You could then arrange for your guide to meet you in Berlin.
Berlin is a great city with many interesting sights. We found the former Nazi concentration camp located just outside the city to be particularly interesting.
Jim