Matte is actually a better finish for scanning. If you scan with a reflective surface than the light during the scan process will cause problems. You can go for a lower dpi, but the higher the resolution the better quality, both in printing at a larger output and bringing out detail in the image. Just make sure you thoroughly clean the scan bed and without damaging the photo surface try to remove what you can. It's always good to give it a good spray with a can of air, both the image and the scan bed. If none of that works than the cloning tool is definitely your friend.