How do I upgrade IPhone SDK from 3.1.2 to 3.1.3

So I'm downloading this xcode 3.2.1 with iphone sdk 3.1.3 (it's like 3gb). I currently have xcode 3.2.1 with iphone sdk 3.1.2. What is the way to upgrade this, do I just install it and it'll install it over the one I have or something, is this even the right way to do this since I'm 开发者_JAVA技巧only trying to upgrade the iphone sdk?? Thanks in advance

Yes, just install it. No need to overcomplicate things.