$50.00 is fucking ridiculous. Do it yourself. I'm assuming you know how to use a screw driver.
As for stance width, take a string and go from your knee to the floor. That's a good place to start.
Angles are all preference. make sure that your backfoot is zero or less and play around to see what works for you and feels neutral. It's something you'll end up changing a lot when you first start riding.
I started with 15-0 front/back and as I started to ride switch more went to 15/-6 and now I'm at 12/12.....
Basically the goal is, to get something that feels nice and neutral/natural when you're standing on ur sn0slider.