Jellings forgot the most obvious:
Get a CD of a distro (like redhat, mandrake, ... [disclaimer: Debian4me]) that is set up to be relatively easy to install, and boot it up. If you don't unplug the slave disk, note that hda will be your new HD and hdb will be the win98 slave. Disk druid should should detect hdb to have a win partition and not touch it, but playing it safe as Jellings advises is not a bad idea.
I would recommend KDE workstation and then post-install apache+php etc from rpm's (redhat packages)
Read the instructions on the CD and the manual for more specific install stuff. For more on dual boot, see the dual-boot HOWTO at the linux documentation project http://www.linuxdoc.org/ Other sites that might contain useful info are
linuxnewbie.org (internet.com's site)
redhat.com
As an alternative, find some local linux freak (or a LUG) who owes you a favour or could do with a case of beer, kilo of coffee or some pizza. Take them the HD and a list of everything you know about your hardware (video card, monitor, etc), and watch over their shoulder while they plug it into their box, do the install and hand it back.
Good luck!