Career critical and 3 days means anything goes.
Google for "sevlet tutorial" and you'll find zillions of examples. Your servlet engine probably shipped with some samples, too. To stick with the "from scratch" theme, start with an empty file in your editor and copy in only lines that you completely understand and know you need. Read a few tutorials and see what they all have in common - that's a good clue to the bare minimum starting point. Make a real effort to see what you can leave out. I just love deleting code!
Couple ideas ... always have the user post or get to a servlet. These are pure java, no html, and well suited to figuring out what the user wants to get or update. Put the results of the action in an object on the session and redirect control to a JSP to generate HTML. These are mostly HTML with just enough script to get data from that object on the session and populate the screen. Be sure to remove the object from the session at end or the session will grow forever.
A neat
pattern is post-redirect-get. The user posts a screen full of updates to the server. The server does the updates and sends a redirect instruction back to the browser. The browser does a get on the specified page which retrieves the data to confirm the update. This neatly separates your update and retrieval code, and allows the user to hit "refresh" on the results page.
Hope that helps! Check in often as you get into this!