You can get a prepaid from the Sprint store, online or from anywhere they sell phones. Somewhere like Walmart, Target or K-mart. Many stores like the 7-12 or the Cumberland Farms also send them. If you do get one shop around for the best deal on minutes because not all places have the same rates.
There are a lot of place that you can find one. The easiest place to find one is online. There are a lot of sites that sell go phones. Otherwise check you local departments stores or Sprint store.
Sprint offers pre-paid phones through their many retail locations. You should google 'Sprint Store Locator' to find a store near you. If there is not a local retail location, you can get help finding the right phone by visiting Sprint's website.
There are a number of different sources to download ringtones for your bluetooth. I would recommend Apple itunes you will receive a variety of genres of music.