Yes, there were changes.
The changes made were not as drastic as in some expurgated shows (even back in the 1970s, things were being removed for censorship purposes). Wikipedia mentions that another 1970s anime, Battle of the Planets, was made with far more revisions to its original series. It also notes that, unlike some series, Star Blazers retained "practically all of its uniquely Japanese characteristics in terms of content, plot, character development, and philosophy."
Wikipedia's section on Star Blazers production covers this pretty well (boldface and -comments are mine):
Principal changes in the change-over to Star Blazers included westernization of character names, reduction of personal violence, toning down of offensive language and alcohol use (references to sake were changed to "spring water," and the Doctor's perpetually drunken state was portrayed as merely good humor), removal of sexual fan service, and reduction of references to World War II, although the sunken battleship ruins were still identified as the Battleship Yamato in dialogue. The most significant reference removed—and the longest single edit in the series—was a section from episode two depicting the Battleship Yamato's final battle during World War II, including imagery of the captain tied to the helm as he went down with his ship. (This section WAS NOT in the bonus content on the Voyager Entertainment Series 1, Part II English-language DVD release.)
The most significant change made by Griffin-Bacal [the company responsible for dubbing/editing] was purely narrative: In the original series the Yamato and its crew were regarded as a single entity, the narrator each week urging "Yamato, hurry to Iscandar!" In English, the significance of the name Yamato as a word the viewers can identify with, signifying the land, people, and spirit of Japan is lost, so in Star Blazers the crew were named the Star Force and became the focus of the show.
— Star Blazers, Wikipedia, March 30, 2013
It seems two of the three references (, ) for this section were lost by dead links (though they may be put back up in the future). However, this reference is still available.