Leaving Typepad

So. I've made the big decision and I'm leaving Typepad for Wordpress. 

I've hired professional help to get the posts over to Wordpress, so the transfer should go smoothly. *FINGERS CROSSED*

What I need help with, dear friends, is now that I have Wordpress...what? I'm supposed to get things called plugins, and I have no idea what they are. 

So instead of spending hours (OK, MORE hours) in Wordpress forums, I thought I'd ask the smartest people I know (that would be you guys) for advice.

What's your favorite Wordpress plugin? Oh, and is there anything I should know before I get the process started? 

I'm begging for advice here. Nothing is too obvious for me. I feel like a total beginner.

I'm so nervous about this. Typepad has been good to me, but it's time to move on.