[CentOS] how to get the source for installed RPM (CUPS)

I would like to change a few things in CUPS, but I would prefer to use the source for the version of CUPS that I already have installed using yum. Mostly because I'm quite happy with the way it works except a few details.

Is there a way to get the source using yum or should I go to http://www.cups.org/software.php and get it from there ?

The version I installed with yum is 1.1.22 and on http://www.cups.org/software.php the best match is 1.1.23.

Or would you suggest I go with the latest version released on http://www.cups.org/software.php ?

This is the first time I feel the need to change something so I'm not quite sure how to start out on this and I don't want to spend a lot of time on the wrong source code.

best regards Ulrik