Change DVD in navigation system

Hi All

hope I am not repeating any thread but I could not find a solution to my problem.

I have a prius 2008 european model, I think the nav unit is under the passenger's seat.

I have located something when I pushed the seat all the way to the front adn I see a black latch/cover preventing me to go deeper and change my dvd.

I see a few plastic screws but no way to easy unscrew them with out breaking them or cause a damage.

Is there anyone out there that could post some pictures and more details on how to replace my DVD and proceed?

I imaging the same applies to american models of 2008.

Thank you.
G