well, i very much doubt its at all possible to have Linux on one monitor and 98 on the other, since that would involve running 2 compeltely different OS's at once. You may need a second system to manage that one im afraid.
Have you currently got win98 installed? are you will to format the system and start from the beginning?
if you want to partition without uninstalling win98, youl have to look for software such as Partition Magic (http://www.powerquest.com/partitionmagic/
). There is similar software available which does the same thing.
If you have a cleanly formatted system then either the Linux installation program will allow you to partition it before hand, and then you can install 98 on the remaining space.