sound like the car has the winter package & luxury package, if it has sport package you can tell by the suspension & wheels.
for the LED taillights you can buy them off Ebay, it's plugNplay, those LED lights come with 2 modules(one for each side) the module is installed in the spare wheel well, they are made by Hella & won't set off a code.
the front headlights are also plugNplay if you buy the Hella one's.
I have dead pixels to in my cluster & will also light to know how to fix it, let me know when you find out.
adding a in-dash screen would be nice but most of the installs I've seen requires you to remove the in-dash tape deck & OBC unit, so if you are willing to give up or relocate the OBC that is your only soulution.
headlamp washers is a option, but be glad you don't have them, I heard they brake or leak.
it's kinda hard for me to answer all your questions because the 99 model was the begining of a lot of changes to E39's.
Maxbimmer Drama, You Gotta Love It