I purchased this used from a seller who stated it was in like new condition.  My question is what function does the plastic have to the unit? Is it part of the touch screen or just for glare?  would it be easy to replace?  The unit seems to work as it should without any issues.

 

I have made a similar dent in mine when the screen touched the "unprotected" gear stick.  After a few tears, I converted this misfortune into a lesson: Always put back the rubber knob on the stick ASAP.

 

It's a bit annoying when sliding your finger/nail on the screen, but it still works perfectly.