For livecds, I'd very much recommend Wolvix or DSL-N. Mostly Wolvix these days. It's full of stuff, and most importantly, ltris and crack-attack for when you're gparted-iting. <3
As for modifying X, for stuff like adding resolutions it can be easier using the distro's native configuration tools. For debian, "dpkg-reconfigure xserver-xorg", and for a bunch of others there's xorgcfg and xorgconfig. I think Ubuntu's got itself a nice GTK app for it as well.
As for desktop environments, I'd recommend GNOME first- coming from Windows, a user might be used to fugly desktops and shitty theme management, but getting into GNOME first can do wonders. It's very intuitive, very easy to use and very pretty. You can even move those panels around by just clicking and dragging. When you start realising how much GNOME holds back by refusing to do some very basic things, it might be time to move on to KDE. At this point, KDE4 might be out and it'll be the faptastic magnum opus for linux this year. <3
Also why the FreeBSD love? It's a neato OS I'm sure, but linux is the horse to bet on. Most hardware manufacturers have just started acknowledging linux's existence- FreeBSD support would likely get a lot of blank stares. D: