You can get source versions of all of the DotNetNuke modules from the Project Downloads page (
http://www.dotnetnuke.com/Resources...ads.aspx). You will then need to create a development version of DotNetNuke, install the source version of the module, make your changes, and then compile a custom version. I would opt to change the name and namespaces used so that your version of F&L won't conflict with the "stock" version.
Chris Hammond, DotNetNuke Corp.'s Director of Training, has a nice set of tutorials on module development and creating a development environment over at DotNetNuke.com. You might want to ease into something like this by viewing our "How to improve a DotNetNuke module (The Blog module)" tutorial.
And, you might want to ask some questions about all of this from the F&L developers over that the DotNetNuke.com forum for the module. They might have some thoughts on how to do this, too.