If you review the iFixIt guide for you system you'll find the very last step talks about the thermal sensor which you will need to remove from your old drive and re-attach to your new HD. You don't need any fan control software,
HD thermal sensor
You still may have heat issues with this HD bigger drives tend to run hotter. This iMac's cooling system may not be able to handle the added heat. As with 'everything 'your mileage will vary' some people don't push their drives that hard, others do. If you tend to push a lot of files watch lots of movies or TV shows in iTunes, you may encounter heat issues. I would strongly recommend using the app 'Temperature Gauge' which you can find in the Apps Store to monitor things. A good idea is to map out what you are seeing now with your current HD and then see how much of a change you see after upgrading. In any case I would not use any fan control software as you'll more likely cook your system than cool it when using it in this case.