For conditioning, begin a walking/running program - something that you can start anywhere. A general conditioning program in a gym can also be of benefit.
Winter is a pretty goodtime for Big Bend and thee Guadalupes. Just pay attention to the weather report and beware of storms.
Basic items are an well fitted backpack, relatively small for a typical day hike, and well fitted, broken in boots or hiking shoes. Clothing should be appropriate for weather conditions and should include at least some sort of moisture resistant, windproof outer shell garment. My recommendation here is the Patagonia Houdini. Some sort of fully visored hat is a good idea.
Learn to use a topographic map and compass to keep you oriented. A good First Aid course is helpful not just in the outdoors, but everywhere - highly recommended.
For further info, I highly recommend the first 131 pages of Mountaineering: Freedom of the Hills which should be available in a local library. Hiking is the gateway drug to all kinds of fascinating pursuits, from mountaineering and climbing to bird watching...
Have fun out there and be safe!!
one or more gifts or other benefits from the co-op.