Skoda Multimedia basic unit (MOST)

Hi all I would like to improove my sound system. But it was very difficult to find crucial information about it. Could you share your experiences\ideas about ?

- how to exchange standrd speakers for better ones (Audio System, Focal or Hertz etc...) ? How to unmount existing speakers ? 

- or connect extarnal amplifier + subwoofer to existing sound system ?

- or do both.

Standard radio is Bolero but there is a need to unmount Skoda Multimedia base unit(I dont know how to take it off ??)  in order to (somehow???) connect signals for external amplifier + subwoofer.

Any thoughts ? experiences ? reccomendations or photos ?