I recently got back from a task in Istanbul. If you need any advice or tips send me a PM and I will do my best to help.
EG; you can buy your visa airside at the airport when you arrive for Â£12.50 but have the cash in Dollars or Euros to speed things along, they didn't accept Pounds Sterling.
If you are offered a Hotel car at the airport decline in favour of a taxi. Taxis are relatively cheap in Istanbul, hotel cars are almost 100% more expensive.
Traffic in Istanbul can be hideous at peak times, allow yourself plenty of time to travel.
Let me know if you have any queries.