1: They are a mixture of COD files(applications) from various OSes, including 7.0 and 7.1
2: They offer better battery life, network locking(less dropped calls), and better support than stock oses
3: A personal recommendation for the 9300|(my device)| would be:
http://forums.crackberry.com/hybrid-...0727-a-737826/
4: Download at the earlier post
5:
http://forums.crackberry.com/forum-f...-guide-579800/ install guide
6: To install means wiping the old OS, but if you are unsatisfied, you can revert to a stock OS at any time.
I would be willing to help walk you through, if the installation instructions are unclear.