Upgrading from 3.2 to 4.0
I'm sure this question is on many lips (fingertips?); I'd like to try out 4.0 and give it a whirl. I've only started using 3.*, so I have a moderate amount of content, but, since its all my documentation, something I'd hate to lose. I assume 4 is the new development path and, although it may initially be rough around the edges, will probably get more attention, developer-wise; seems better to jump on the band wagon now.
Questions on upgrading:
1) Can I upgrade over a copy of my existing 3.* database or does 4.0 have a new schema that may make this incompatible/generate problems?
2) If I don't go this route, once I determine that 4.0 is for me, is there a way to copy over existing data, permissions, etc from 3.* to 4.0? Or, even better, sync the two?
If there is documentation for this already, please point me to it. If someone in the know is willing to walk me through it and answer questions, I can volunteer to at least start documenting the process in return.