|I've never needed to set up something like that so I can't give you precise steps. Plus, this type of setup is usually accomplished via 'trial and error' by the user.|
Anyway, even though you want to install 98 you need to set up dos support for the devices first as config.sys is a dos file. Check these links for info on that:
You can also check at bootdisk.com.
If that works to allow you to finish the 98 install then you can remove the modification to config.sys and look for 98 drivers for the external cdrom.
It ain't gonna be easy. If you get it figured out it'd be a good idea to post back exactly what you did to help others who for some reason want to do the same thing.
Real men don't use AntiVirus; they just reformat