My 2004 Impala suddenly lost all power

My 2004 Impala suddenly lost all power. It as working fine 3 days ago, then last night I went to go to the store and pressed the button on my keys to unlock the door. Nothing happened. I tried the trunk and nothing happened. Luckily the driver door was already unlocked, so I got in and turned the ignition.

Absolutely nothing happened. None of the lights in the car turned on, not even the overhead light when I opened the door. I even tried pushing the button inside the driver's side of the car to open the trunk and there wasn't even any clicking.

This morning I got a neighbor to try and jumpstart it. No change from last night. Even with their cables attached to my car, not one light came on in my car, the engine would not turn over even once.

I've asked a couple people I know and they seem to think it's one of a couple things:
• Dead battery
I've taken a look at the battery for corosion around the + and - terminals and it looks fine.
• Blown fuse
I have no idea where to look for fuses

I'm freaking out because I'm in the middle of negotiations to trade in this car for a minivan, and I'm afraid my car is worthless now. So my question is two-part:

1. How do I get my car to start again, and
2. If I can't get it started again, is it now worthless for a trade in?

I don't know very much about cars (obviously or I wouldn't be here), so any help (in layman's terms) would be appreciated.