Hello Clayton,
Welcome to the Forum.
Seating.
It does (at least) mean changing (some of) the rails.
Your model will have four. You need five for the 1.5 plus 1 seating.
I have never done it, but on the principle that putting things back together is never as easy as taking them apart, be careful.
However, I would expect any converter to be able to do the job; although they normally only take them out.
They may also be able to supply the seating too.
Headunit.
Can be done, ensure you ask about the cameras and steering controls being retained before agreeing to have it done.
Curtains.
My electric curtains are 'jerky' and do not perform perfectly.
Unless you like to 'play' with them it is of no consequence.
Park up, push button, manually adjust.
I had thought of WD40 to lower friction; but friction may not be the cause.
They do close and open almost instantly, I would have preferred a slow smooth action.
Let me know about the furniture polish approach. I hope it works for you.