i am installing kde 3.4 right now. i think the easiest way to do it is with the program konstruct which is available at
http://developer.kde.org/build/konstruct/. it will download all of the necessary files, check their integrity, and make them.
dual booting is pretty simple, just allocate separate partitions for your installs. they can share the same swap space. then on whichever install you make second, run "lilo" and it should detect your installs. "grub" is another boot loader.