Once you've scanned your photo and have it on your computer open it up in Photoshop and duplicate it.
1. Dust and Scratches
Next, go to Filter>Noise>Dust and Scratches. This brings up a window with two slider controls: Radius and Threshold and a preview window. If you only adjust the Radius slider the dust and marks vanish but the edges of the image soften making it look like you've smudged it. However, if you adjust the Threshold too you'll see the detail slowly come back. Don't take the slider too far though as the photo will become blotchy. Adjust both sliders until the dust is removed but the sharpness and edge detail remains then click OK once you're happy.
2. Lasso Tool
If you still have a few scratches that are visible select the Lasso tool and make a rough selection around the problem area. Once you have a circle of 'running ants', select the Dust and Scratches filter once again. Adjust both sliders until the marks are removed but there's still enough grain left to ensure the adjusted patch blends with the rest of the photo. Take too much away and you'll have an obvious smooth patch that stands out from the rest of the image.
If you want to add a slight colour tint to the image one of the easiest ways to do this is to click on the adjustment layer icon at the bottom of the layers palette and select Photo Filter. There are various pre-set options to choose from or you can select your own by clicking on the box filled with colour. To adjust the intensity of the filter
move the density slider to the left or right.
Photo with Filter applied: