Hello,
There are several ways to go about this. I would encourage you to think about what computer is going to be your 'server' and what computer is going to be the 'client'. REason? You can run into trouble with backups, remembering which file is "latest", and run into version control problems.
You mentioned that the windows 98 machines can see your linux box, so the usual steps about checking your IP and other things are already done.
Under windows 98:
* Create a sharepoint. This means basically enable a folder to share. Decide security. If you are going to have a username / passoword combination, have that created.
* Grant permissions to a user for that sharepoint. It does no good to tell me I can borrow the car, and then not give me any keys. Same idea here. Make the share, and then set the permissions
On Linux Box:
You will need to be root user to work some of the utilities; others will not require root.
Look in /usr/bin/smb* for the smb utilities. There are programs called smbmount and smbumount. Those tools will help you mount up the share from win98 to the linux box. The linux box will not see it as a drive letter... rather it will show up in the file system and you simply "cd where/my/share/is" and you will "land" there.
If you would like more help, we need to know what version of samba you are using, along with the permission structure of the W98 environment is.
Christian