For question 3 the door panels are held in by small plastic rivets that have a nasty habit of breaking when you pry the panel away. Once you've freed the rivets you must lift the panel UP and out as behind the door handle there is a clip which slides down over a retainer on the door. You will also have to unhook the door opening mechanism. Also be careful of the window switch which has very short wires. Trim can be expensive so weigh up what it would cost you at a trimmer.
I had my washer bottle pump out last weekend. I have an earlier model 525i but if it is similar it is in the front of the washer bottle and simply pushes in so you should be able to just pull it out of the bottle.
Cheers
Wingman
'89 525i/A Exec 193000kms
'94 Subaru Liberty AWD Wagon
Looking for Merc 300TE
NSW, Australia