There are couple of ways to make life easier with CVSdiff. But here is one that is really good.
First if you haven’t, install meld:
sudo yum install meld
meld is basically a diff viewer and pretty good at it 😉
Now open meld from the menu or from the terminal. And then select New. In the dialog box that appears select “Version Control Browser”. In the Directory box, browse to the folder where you have the code checked out and select ok. And you are all set.