Communicator 7 - When I plug in my personal headphones into the computer jack will I need to change any settings to use this application?

Yes - When you plug in your headphones you will get a message saying "which device do you want to use?".  Choose from the list: "Dell Speaker Out".  This setting will allow both your personal headphones and your Communicator 7 headset to work together.  You will hear a ring in your personal headphones, and then be able to put on your headset on to answer the call, without the other sound playing to your headset interfering.