Surprise: a book set in the pre-Civil War South with a black man as one of the main characters deals with the theme of race. We're shocked. But seriously, Huckleberry Finn tackles some major issues. Remember that, even though slavery had ended by the time Huck Finn was published, the whole country was still deeply racist. Is Twain anti-racist? Does he truly believe that black people are equal to white people, or is he only pointing out the South's hypocrisy? And would Twain have had black friends?
Change shmange. Huck Finn is just as racist at the end of the novel as he is at the beginning.
Huck totally learns his lesson over the course of the novel, and he comes out the other end much more tolerant.