Yes. As far as I know, they have the best prices for model railroading. Unfortunately, there's no free shipping, but it's not too expensive just to pay for standard ground shipping.
Actually, you can have one power pack for both tracks, but you still need 2 separate speed controllers to control the trains separately, but you can connect them both to the same power. Also, to answer your second question, just look up a video explaining the difference between DC and DCC.
