1) go to your mandrake control center and you can partition your drive in there
2) to change your icon themes, you can gop to your mandrake "start" button -->configuration and then KDE style , or something like that. There you can select different icon themes. To install custom icons, go download them from somewhere like www.kde-look.org.
You put them in a directory somewhere. The website will tell you where, but I believe it's something likle /usr/local/.kde/icons, or something like that. I'm using WIndows XP at the moment so I cannot clearly walk you through it.
3) there is a way to make firefox your default. Just search the forum as this has been asked many times by other people. I'm too lazy to look it up for you.