They edited the profanity, the nudity, and for the sake of fitting it into the time slot, a few conversations. They really didn't need to cut the violence, but there are some scenes where they only flash on it, rather than have the camera linger.
Music from every season (from season 1 to season 6) can be found separately for purchase on Amazon.com. Each season has its own released official soundtrack (the soundtrack for seasons 2 and 3 were released together in the same disk) Music from season 7 will be released sometime in the future as well.
You're in luck! Someone has. Television Without Pity has excellent detailed summaries that far outdo anything we could type here. You can click this link to get there. http://www.televisionwithoutpity.com/show/dexter/recaps