I am installing my audio system in my 1999 impreza plus (the wagon version) and i want to check the speakers in the front and rear doors.

 

What are the size of the speakers that fit in the front and rear doors (in mm) and is the tweeter also replaceble?

Then how do i get there, removing the whole door trim by removing the screw at the lock and one in the middle of the door plus prying some clips around the door?

Supposily the connector in the dash showed lots of wires (for 4 speakers) should i assume the wires are indeed already present in the doors (front i think rear i dont know)

You'll have to remove the door panels to get access to the speakers. It's a matter of removing a couple screws, and popping loose a handful of clips around the edge of the panel.

I have 6.5" speakers in mine. I imagine yours would be the same.