GDisk is a very powerful version of Fdisk. It's really cool, but rather complex to get into. It's best you read about what you want to do in the help docs with the program. If you can't find what you are looking for, ask me a specific question on it and I'll give you an answer.
You have to boot to a floppy first so you can set the machine up like dos. once you have the floppy configured, you use that to build the boot image for the DVD. There are ways to make the boot able aside from using a flooppy emulation, but I have never looked into it cause the way we do it works.
I'm leaving for the day, so let me knwo what I can help you with.