Questions about Kindle jailbreaks.

I wanted to buy a kindle an have some questions about the jailbreaking.

1. Can I just buy a Kindle from Amazon and jailbreak it, or do I have to look for a specific firmware version? If so, should I buy a used one, or do you have any other recommendations?

2. What is your experience with the internal space on the Kindle? I know it has 16 or 32 GB, but I don't know if that is enough. Is there any way to "stream" books from a NAS without first connecting the Kindle to a PC and swapping files?

Thanks in advance :)