The actual v3 (and other v phones) screen is underneath a clear screen
"window" that says Motorola across the top. After you've had your phone
for awhile (about 9 months in my case) you may notice dust under the
window even though there are no scratches on the exterior. If this
happens or if you manage to scratch up your screen, it can be easily
replaced.  I just did it today and it took only a few minutes so I
thought I'd report it here.

The covers/windows cost $9 so I bought a few along with a nice pair of
tweezers and a plastic "case removal tool" from www.cnn.cn. My order
arrived from Hong Kong in less than a week.

How to do it:  To be safe, I removed the battery. Next I used the
pointed tweezers to pry up one corner of the window. Once I got it
lifted up a bit I slid the plastic removal tool under and along the edge
of the window to release the adhesive. Once I got one side done I simply
lifted it up and peeled it away. All of the adhesive lifted off with the
window but if it doesn't make sure you remove any left in the phone.

Next I used a lint free cloth (a chamois is perfect) to clean the
actual surface of the screen itself. There was quite a bit of dust.
Don't rub or press hard! Be gentle! I also used the tweezers to hold a
small piece of paper towel to clean the dirt from around the perimeter
of the opening in the case where the window sits.

At this point I put the battery in just to make sure that all was well
with the screen. It was fine so I removed the battery again to finish
up.

With everything sparkling clean I lifted the new window off the carrier
and set it into the opening. It fit in perfectly so I used the cloth to
gently press down around the edge to seat the adhesive. The last step is
to peel off the plastic film (like you did when the phone was new) and
admire your new crystal clear display!