The headliner fabric you can get an almost any upholstery store. I wouldn't use the 3M spray adhesive, though. When it gets hot outside, the fabric will start to sag, at least in my experience. Use Weldwood Contact Cement. Once that stuff sets, that fabric will never come off.
About the mirrors, just make sure that when the window is up it won't hit the mirrors. I'll have to look in my service manual, 'cause I can't remember at the moment how to remove the triangle.
Front speakers are 4"x10", rears (not in the headrest) are 4"x6". I replaced all four with Pioneers. There aren't many companies these days making 4x10 speakers, the selection 4x6 isn't too bad.