Law school is tough, no doubt. Although you posted this last week, and thus presumably your crisis is over, in these types of situations, there is one word that sums up how you should approach everything you need to do: Triage. That's the concept employed by emergency rooms wherein the sickest people are seen first. For example, in your situation, I would recommend that you write the best brief that you can within a short timeframe. Let's say several hours. That was probably for your legal practice class, and most schools don't give you a letter grade in that class. I'm not saying you should blow it off, in fact I belive it's the most important class in law school, but grades are the most important thing right now, especially for a 1L. So do what you can, and move on.
Then I would quickly read through your class material or maybe even ask a friend for their notes on the cases. You can read these cases later when you prepare for your final. I would then use all your remaining time to study for your final. Create your outlines and slam this one out of the park. When it's done, you can focus on the other things that you've fallen behind on.
And ignore the first poster to reply, apparently he hasn't talked to many people in law school because everybody has gotten this stressed at one point or another (or at many different points). It's part of the process...