Peter, if you're just changing your stereo then there's nowt to it - if it's a modern car then it'll either be a standard ISO connector at the back of it or a manufacturers own connector and Halfords sell adaptors to convert most manufacturers to standard, they also have all the various key/pins for removing them. Aerial - if it's duff just replace it, just a single cable though it might be a chore if it's routed somewhere daft..