Modifying xorg.conf?

I'm still trying to get my laptop with integrated S3 savage chip to use dri. I've found some good resources, but I still have a couple of concerns that I hope someone can help with. Firstly, I have to change settings in xorg.conf but I don't want to mess up SaX. For the record, SaX tells me that 3D accelleration isn't available for my card. Is there a safe way to modify the xorg.conf file? I'll send another email for the other problem, it's only remotely linked. -- Paul