D.C. Help

Okay folks this girl needs a little help! I'm leaving for Washington D.C. in just a few days. I have a conference there for work. I will be there Sunday-Wednesday. So I need a little D.C. help. Here are my questions. If you have any answers please leave them in the comments.

1. I have very limited time for sight seeing. Only after 4:30 each day. In that limited amount of time what do you think I MUST see or do.
2. Know any great restaurants?
3. Know any great shops?
4. Is the metro safe? Am I going to be totally lost on the metro?
5. Do any of you live in D.C?

So those are my questions.... Can you help this Kansas girl make the most of her big trip to the city? I want to make the most of my time. While the conference is my priority I want to take advantage of all the free time I have.

Thanks!

Clickin Mama