in my experience...a p3 500mhz processor is a bit slow to be running kde which can be a totally bloated environment to run. the swap shouldn't be a problem, cuz you have 512 of ram. i have 512 of ram as well, and my swap is never touched. what i did when i ran suse on a p3 was to use a lighter window manager. fluxbox is quick and zippier, and fully configurable, although it's something you need to get used to. being new can be a bit daunting, but if you stick with it and are willing to learn as you go, you should be fine
i've never used mandriva/madrake, but i would think it's the same as the others...you might have a choice of which windows manager to use when you boot. look around and see if they aren't already installed. suse and slackware install a few by default, so i would think man would too.
as for a nice tutorial...rute
is an excellent start...