There isn't a manual focus lens or body in the store that hasn't been tossed around by him.
He and I have the same philosophy on equipment.
Too bad I didn't listen to him when he was saying that "plastic can be rugged too, but it makes the camera lighter and you can take it anywhere".
Don't get the filter. For 10 bucks it will degrade the quality of your image.
And also, it's almost impossible to really scratch a lens. Scratches only happen to fisheyes when they're dropped on the asphalt. And those scratches don't affect the quality at all - only resale value.
But since you got it for 80 bucks, you're not planning on babying it to keep the resale value.
So just leave it alone and don't use it.
I'll keep that in mind if i buy from him! Exactly to the right. What do you think of those Metz flashes there?