Like most of the folks that hike the AZ Trail, I use the USGS maps for the area. For planning, I prefer the 1:125,0000 scale and if I feel the need for more detail I will get the 7.5' sheets. Map expenses can mount up quickly if you get complete coverage of 300 miles of trail in the 7.5' maps; that is why I prefer those that cover a larger area. You can easily hike across a 7.5' map in less than a day. Here is the USGS map website, check it out.

usgsstore.usgs.gov

Unless you plan to do mostly cold weather camping, a 0° bag would be more of a liability than an asset. Sleeping, or trying to, in a 0° bag when the temperatures are in the mid 40°'s is hard. You would be better off buying a 15° bag and wearing clothes in it if it gets too cold if you only anticipate a few 0° days. I have done a lot of mountaineering, both summer and winter, in the western states and have seldom had need for my "Arctic" or 0° bag. On many occasions I have taken it on a trip and, as I lay in it, sweating, wished I had taken my lighter bag.

Buy a bag that will handle most of the conditions you anticipate, not the worst. And remember, sleeping bags come warm, light and cheap: you can choose two of the three in any bag.