Remove head unit toyota yaris verso 2001 + change stereo

[River Song]

Hi,
I am trying to remove the head unit of my yaris verso 2001 model. But I am afraid if I use to much force it will break. Is there a trick to it?

The reason I want to remove is to change the stereo. It only has radio and a cassette player. Do I need additional stuff besides the stereo I just bought to make it work? Is there a complete user manual for the verso 2001 where these things are explained?

Thanks in advance :)

Update
I figured out how to remove the top panels, kind of, but I still can't figure out the bottom part (unit with cassette player ).