it's not HARD, but you have to consider your knowledge.
Gentoo is for "experts", I think you can get a not-so-hard procedure with the liveCD and install from that. You can download the ISO and get the manual printed.
You can download from here:
http://gentoo.mirrored.ca/releases/ppc/2004.1/
There's the liveCD and the stages ISO's. I suggest you to read the install docs before even starting to download.
Personally I bought the liveCD online and got it delivered at home (this way you also support the project).
Another solution is YellowDog. You can download it here:
http://www.yellowdoglinux.com/resources ... rors.shtml or buy it online and support the project.
I heard good things about it, but never tested myself.
The difference is that gentoo ALSO support PPC, yellowdog is FOR PPC.
One thing you should also consider even before starting is where you're going to install. You will need a separate partition.
- andrea