How to create a ditribution with own preinstall config dialog?

Dear all,
i want to create a small ISO image with a basic system and my own rpm packages.

Additionally i want to replace the preinstall configuration dialog with a personal one, which should replace some of the configuration pages and add some new.

I have searched for detailed information and tried out the suse studio, but i have not found what i was looking for.

Is the config dialog opensource?
What packages will i need to install?
Where can i find the doku, source, templates for it?

Kind Regards