The fine print is that you have to buy everything from SW at retail pricing there. You can easily get better deals on the system or buy just their headers with a different exhaust and save a boatload more money.
I looked into driving up there for the install. They quoted me a great price on the header install, since I already had headers, if I bought the rest of the system from them. I ended up getting a different exhaust though, which killed this option.
Deals like this are pretty good but if you're driving from a ways out the 2 day install time means hotel, rental car, meals and other stuff. Just as cheap to pay someone locally to do the work if you can find that option.