All my advice on Istanbul can be found at the following site:
http://www.virtualtourist.com/m/71f79/1c0a38/
As for safety, Istanbul is much safer than nearly any other city in the world
of similar size. All types of crime are far less frequent there. With regard to
terrorism, there have been a few bombing incidents lately that I'm sure you've
heard of, but I'm not aware of any attacks targeting tourists. For what it's
worth, I would gladly return to Istanbul now without any fear for my safety.
Feel free to email me with any specific questions after you have a chance to
look over the information on the web site I listed, and enjoy your trip!