.. So how do I actually find the burial chamber?

After you've met everyone and read Jon's notes --

How do I get Jon's notes?

-- go into the tomb and concentrate on tunnel 3.

There are a couple of puzzles in this tunnel, but there's only one you can solve right now --

-- in the left wall of the last chamber.

How do I solve the Queen's Tiles puzzle?

Wow, a whole new door! Let's get on in there --

-- but maybe it would be nice if we could see. Did you explore the antiquities tent yet?

If you don't already have it, you can find a flashlight.

Where is the flashlight?

Using the flashlight from the left table in the antiquities tent, shine some light in a dark place --

-- and all kinds of odd things happen.

Opening the Sarcophagus