White Widow is certainly not a good strain for beginners, but as long as you've got some experience and you're willing to put the time and effort into it, then you'll be fine, and you should end up with some fabulous bud. I recommend getting more educated on everything having to do with growing (highly recommend the Cannabis Grow Bible). Is that one plant the only grow you've done? If so, I wouldn't recommend WW quite yet, but maybe after another grow or two.
I plan on buying from seedboutique.com soon myself...I've heard nothing but good things about them. Yes, feminized means they are (supposedly) all female. If you're growing fully indoors, then I don't see a huge advantage in that to be honest. That is personal preference, I guess. I would just go with the Nirvana WW seeds (cheapest and high quality) from seedboutique if I were you, but you should definitely research each seedbank more.