My husband and I hope to go to Istanbul in May, and would love to hear from others who have visited Istanbul. We've well-traveled, but this is our first time to Turkey. We have the usual "tourist" questions: Is it easy to navigate the city on one's own, or should we hire a tour guide to take us around? Is seven days a good length of time? What would be a ball park estimate for budgeting lunches and dinners? Are there any suggestions, observations, advice which you can give us?