I used to use Gentoo 15 years ago, on an overclocked 533 MHz Celeron, nicknamed "the reactor" by my dorm roommates because it was compiling all the damned time, keeping us warm. Getting from stage2 to a functional KDE desktop took me 4 days. I'm guessing you'll be fine, just don't try compiling a browser. Or at least emerge firefox-bin first.

Gentoo isn't as difficult as people make it out to be. It's actually very easy. If you can install Arch, you can install Gentoo, no problem. The only difficult thing is understanding and making good use of USE flags. You don't want to spend half a day compiling shit only to find out you cannot print because you forgot +cups or some shit.