Yes. All you have to do is go to the Sites tab for that campaign, delete the site entry, and re-enter it with the correct analytics information. It only takes about 30 seconds, and it will NOT delete any of your keywords / URLs or any other info you've already set up. These tabs are entirely independent of each other.
You can actually enter landers and keywords without entering the site information whatsoever. It's entirely optional, and is only used to attempt to automatically pull in different types of data for larger sites that you might control.