Shadow Walk concealment lasts until the end of your next turn. So you can Eyebite someone(and assuming you hit), move 3 or more squares and make a Stealth check(at -5 for moving more than 2 squares). Assuming that sticks, you will be hidden from that guy until the end of your next turn, unless you do something to break stealth, or re-stealth.
As for your questions regarding Swordmage stuff, I suggest you download the beta of the Character Builder. It only goes up to level 3, but it's great for concepting characters. It has pretty much every feat/class/power/thing around, within those levels, anyway. There are still a handful of calculation errors, but that's why it's a beta.
Character Builder Beta
Later!
Gruns