Fantastic bobs! We're thinking of doing it as well. From what I can gather, it's quite expensive once you get there. Goods sold to tourists are expensive - such as clothing and hand-made items. A week will be plenty for you to see the sights. The full trail takes about 4 days, but the shorter Sacred Walk takes 2. Apparently the walk to Vilcabamba La Vieja is one of the most beautiful and finishes at the hub of the Incan empire. The full trail costs about $50 each. To prepare yourself, make sure you're fit & have the right footwear. Sundays are the quietest days to start out.