So I noticed 2 GPS options on my Droid X. They are: 1. Use GPS satellies 2. Enable Assisted GPS First of all, what is the difference between these two options, and second of all, can I be charged extra for its use with an unlimited data plan? The second option says something about "preferred service" so I am a little scared to use it because I don't want to get gouged on my bill. Thanks in advance.