I'll take a shot at answering your questions:
1. Since you need an unlocked unit it will depend on whether you are in the U.S. or ordering it from overseas. If ordering it from overseas, unless you have someone in the U.S. that can purchase it for you, you will probably need to order it from Adam at
www.GSMPHONESOURCE.com already unlocked.
2. You only need your carrier to provide the BIS service and a BlackBerry data plan to access your pop3 email accounts. The best way is to forward your mail to your BlackBerry address (fastest) but if your pop3 account doesn't allow that, then you can use your web service account to poll for your email. You could also sign up for one of the third party BES services since setting up your own is quite expensive.
3. The major limiting factor if you are using an Apple product running OSX is the ability to install upgrades and applications to your handheld. You really need a PC to do this easily. There is a third party application for sync to your PIM (search the threads and you will find it).
Merry Christmas and enjoy!