You have to atleast be rooted then you can us Backup for Root to backup some of the phone...
You can also use Astro, File Exlorer, Linda File Manager after rooting to save most of the Phone Data to your SD.
Make sure you look at the Camera/Power up to see if you have PVT or DVT....read up on this as I have hear you can brick your phone pretty easy with DVT version...PVT is pretty safe...but I read that here...so who know if the person even knew what they were talking about
Not at all difficult, if you need my help just ask. Use the guides in the site. I know some of the files may not be there and are hard to find, but I can help you out with that, too.
...I'm not entirely sure but when I put my SIM card in the G1 from a Sidekick 2008, it transfered all my contacts. But then again, I dont know if I just got lucky or if it actually does that.