As far as the windshield is concerned, here's what I would do:
1) Thoroughly clean the windshield with windshield stripping paste, Bon-Ami or toothpaste (paste not jel). You need something that is very mildly abrasive to remove the film that is there.
2) Next clean the windshield with rubbing alcohol or Windex. Always buff the windshield with a perfectly dry paper towel after cleaning it to prevent streaking.
3) Thoroughly clean your windshield wiper with Windex or alcohol. Clean your wiper each time you fuel your car to maintain it. You can just use a moist towel at the gas station.
4) For a final touch. Look for a product called "Vision Blade". And apply every 3 or 4 months.
5) Change your wiper blade each spring.
This process totally solved my smearing windshield on my E430.