I don't think minor scratches affect the value except major ones.
One of the question ask about the enclosure like "Is the enclosure free of signs of bending, major dents, and deep scratches? Are there zero signs of liquid damage? Do all the buttons work as they should?"
Another one ask about the screen "Good shape means the touchscreen functions normally and is free of major cracks, chips, and scratches. Damaged means, well, it’s damaged."
To get a quicker estimate, you can take it to an Apple store which they can evaluate it for you and if you like the value they can send it in for you and you will receive instant credit via gift card.