Concerning the scanner.
My epson does not scan from the epson itself, I use Xsane for that.
In order to have it enabled look at this post at the bottom: http://forum.sabayon.org/viewtopic.php?f=56&t=27828
Epson does have linux drivers but that are all deb or rpm.
Normally you should be able to install rmp packages on Gentoo when installing the rpm manager as far as I remember.
Concerning wireless, it was sometime ago I installed it like that, I use KDE and in systemsettings it has some tools.
Else you can make it a network printer by connecting it to your router and from there you can add it to your system.