I'm a bit confused about the Leapfrog iQuest. I bought the iQuest for my DD. I also bought Mind Station. I see that they sell cartridges for certain topics (science, social studies). My questions are: does the iQuest have any information already installed on it (other than the PDA functions)? Do you download the info through mind station or cartridges or do you need both? Since I already bought the mind station do I need to buy those cartridges? Thank you!