Firstly - deep breath, it's gonna be OK.
A dissertation is a massive undertaking and anyone that has written one, would have had the same moments of absolute terror and panic.
Good news, you have over two weeks!
The way it was suggested to me - I'm guessing you already have a topic? I'm also going to assume that you've done most of the reading/literature reviews (what others had said)? In that case, congratulations, you have already done more than you probably expected.
In a 8000 word dissertation, around 1000 will be your intro, 3000 your literature review, then you findings/the main bit 3000 and finally a 1000 conclusion.
Write your conclusion first - what have you concluded as a result of doing the research?
Now write the introduction, what are you going to try and prove? As you have already written the conclusion, you should find that your intro tailors itself back to your conclusion automatically.
Now the literature review - what have others said about your hypothesis?
So all you now have to do is the middle 3000 bit, which is the research you would have done towards the hypothesis.
You can probably do this in just over a week. That gives you a couple of days to then put it away completely. Then it's time to review and edit. Contrary to belief, a Masters doesn't have to be full of long words. As long as it reads well, makes sense and answers your question.
And remember - absolute worse, If you have already completed 120 Masters credits (which again I am assuming as you are at the dissertation stage) - it means you could, even now, exit with a Post Graduate Diploma.
You are gonna be OK.