Looks like there's a clock there at the bottom below the HU. Do you really need that? Since there looks to be one on the HU as well? My vote would be to take the clock out, move the HU down to where the clock is, and use that space above to mount the screen.
Mounting flush shouldn't be a problem since it looks like you'll have ample space depth-wise there. You'll definately need to use some sort of 'filler' or compound to make it look good though.
What you'll need to do is take measurements of the screen both in and out of it's casing. Then take measurements of where you're wanting to put it. Play around until the numbers line up and then use that as a starting point.