SNIP SNIP SNIP
yes i would swap out the top of the camera
and yes, i would tell the potential buyer.
better yet, i would sell the camera as is + dented
and tell the buyer that i would be happy to swap out
the top for him / her for a few dollars more.
i would also assure the buyer that this would not affect the performance
in any way, and offer them a money back guarantee so if there was a problem
in 30 days because of something that happened when the tops were swapped out
they could return it or get a partial refund to have it professional repaired.
what is the point in being secretive ... if you are confident your work will
cause no problems, say so to the potential buyer and then stand behind the work you did
with a grace period.