FC3 by default starts GDM, which is Gnome. You can fix that a number of ways, none of which are pretty, find the /etc/rc.d/rc.5/ file that starts gdm (google ... don't remember) and set it to kdm instead (rem the first if statment'd do it). Alternatively, live with GDM, but click on session set to kde, the log on. next time round it will ask if you want to run KDE and set it as your default (or something else).
Even if you switch from gdm to kdm, you will still need to reconfig to kde manually (via session), so you might as well leave GDM as it is (far less hassle) and get it to bounce you into KDE.
How linux works... Understanding the Linux Kernel is a good book, but probably not what you are after, consider the following links:
<- the linux subset of google
<- good book (though debian based from memory), there is an online version as well, but i can't find it
<- the linux documentation project
you've already found this place, and by and large we are friendly. And whatever you do, don't buy a Linux <insert distro> unleashed, they are handy references but from a usage point of view they are a terrible waste of time. I loved Linux in a Nutshell (O'reilly) but until you have a grasp of what you want to do, and what program might be the best, it's not going to do you much good, (Check it out in a shop, see if it does it for you, but realise it isn't very differnt to the man pages you already have).
Probably check out: http://www.oreilly.com/openbook/
while you're at it.
In conclusion "The art of unix programming" is also quite good, but possibly a little of topic for you. Like most things you can't be told how things work together, you will have a day and suddenly it will be quite clear, and you won't know how you got there.