There are lots of ways the New Testament is different from the Old. That's why it's called "New". A testament is another word for "covenant", and the book of Hebrews describes this by repeating the adjective "better".
But there are also lots of ways that the New Testament simply builds on the Old, transforming it, fulfilling it, colouring it in, but not replacing it. In fact, this is so much so, that when we read the Old Testament we rarely have to ask: "What is the complete contrast for us?", but far more often ask "What do the lessons here look like for us today?"