Save your money...the problem probably isn't your video card. Take a look at this url:
http://aroundcny.com/technofile/texts/tec041501.html
I think you would be better off upgrading to Windows 2000 or XP. With 512 MB of RAM either will run very well on your processor where W98 doesn't really know how to handle more than 256 MB anyway.
Good luck.