Welcome to RP. This might not be the best way, but here it is.
I used the channel mixer, set to monochrome, red 100%, green to 10% to add a little contrast. Made a duplicate layer, and used dust and scratches filter at 4 radius and 4 threshold. Made a layer mask on that layer, and filled with black. This brought me back to what it looked like before using the dust and scratches filter. I only worked on the face a little. Painting with white, at low opacity, around 15% and using a soft brush(while the layer mask is targeted) on the areas that needed improvement, brought the image to where it is now. Painting with white will undo what you painted with black. I forgot to add that I used a curves adjustment layer to improve the tonal range. Color can always be added if you want to add it.