You don't need to use Entourage if you don't want to. PocketMac can sync contacts, calendar events, tasks and notes from a number of different sources on your Mac (including Entourage or the built in Mac OSX applications e.g. Address Book, iCal, Stickies).
If you're already using the Apple applications to manage your contacts and schedule then I suggest you keep on using them.
Your email isn't synced through your Mac - you download your email online either through the Blackberry Web Server (an internet site lets you configure the options) or Blackberry Enterprise Server (configured by your systems administrator).
You do need to buy PocketMac for Blackberry - available from http://www.pocketmac.com/
or it's sometimes available free from your provider (I got my version free from Vodafone in the UK). Make sure you install PocketMac from an administrator account on your Mac.
Good luck - any problems, just post your questions on this site. There's a few of us Blackberry Mac users out here who can help!