If you wanna get things prepped now, get yourself a partition to install to, just make a blank one using whatever partitioning program you choose (in mandrake, there is nothing better than diskdrake IMHO).
Then, before doing anything, read through the install docs from www.gentoo.org
at least once, and get a feel for how things will go, then, as you are doing them, it won't be such a surprise.
Really is different than any other install I've done, however I wouldn't claim it to be "hard" by any stretch, simply different.
Good Luck, and I hope it's everything for you as it has been for me!