On Gentoo, there isn't any install app that does this for you automatically. However, there is a liveCD you can download and burn that will get you started. It's still text based install. But in all honesty, I don't really think this matters, since the text install is soooo easy. Just follow the directions.
On a regular PC, I can understand how this can get complicated, since everyone's systems are vastly different from one another. But on PS3, there's really 2 different things. Either install it on a 10GB partition, or 50GB partition. And that's about it.
Also, on Gentoo's PS3, stage4 tarballs are available online. So, in my opinion, the install process is much quicker than the CD. Just follow the official install instructions, and you'll be up and running in about 30 minutes.
http://overlays.gentoo.org/proj/cell...allGentooOnPS3