LV Zipper Pull Replacement?

Yup, you definitely can. My mom had hers replaced in her Speedy 30 back in the 90's because it was sticking. Just go in and ask them about it, I'm sure you can have it replaced for tarnishing too.
 
I had a missing zipper pull replaced for $35. I believe you can get pretty much anything but the main fabric of the bag replaced if the bag isn't too old. 'Services' on the website has quite a lot of information on repair work.