1. Knoppix is a live distro, meaning it runs entirely off of cd and does not write to the harddrive, nor allow you to write to the hard drive in it. You can only read. Although there is a way to install knoppix as a permanent distro, and you end up with something based off of debian.
2. I don't know who told you that about red hat, but IMO it's the perfect distrobution for a newbie. But if you want something more modern try fedora core 3, it should configure everything for you. It gives you a default setup as having a gui but its not hard to get "under the hood" with any linux distrobution.
3. First download gaim. Then install it.
If you install something like Fedora it should come with gaim (on gnome...) and some sort of irc. But to install it from sources you would do something like
tar -zxvf gaim.tar.gz
As for IRC, download xirc (its probably installed already though), and do the same installation procedure as gaim (most likely)
4. I'm sure you can. Try getting a real distro up and running first though.