As long as you put the new Kindle on the account your collections are on, your collections will be on your new Kindle when you sync. With the books you are out of luck, you will need to download them individually. However, they should go right back into the collection(s) you have them in.
When you deregister your K2, all of the books you have on there will remain and be usable, until your friend deletes them, or something happens to the Kindle that requires a factory reset.
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