Edge Pro Apex

After years of getting my knives professionally sharpened I bit the bullet and bought myself an edge pro for christmas. When it comes to knife sharpening I definitely fall into the noob category and need some guidance from people who have experience with this thing. I understand the basics and put a nice 15 degree edge on some old henckles 4 stars I had packed away in a closet, but before I go to work on my shuns I have some questions. Should I be trying to keep the factory edge, or should I set a new edge? If keeping factory specs, how do I determine what the angle is? Do shun knives come with a double bevel and how do use the edge pro to make a double beveled edge?