I'm helping a friend who just bought her first home (built in 1920). There is a small spot on the side of the roof near the peak that was damaged a bit by an old tree that is not there anymore. All the damage seems to be mostly cosmetic. As far as we know there are no problems yet with water damage because it is all over the overhang only like 4inches tops. The copper "L" shaped flashing (i don't know what else to call it) has been bent quite a bit and pulled away from the edge and the edges of the tar shingles have been worn away 2-3 inches. That's really it... She said she has been told that there are only three layers of tar roof shingles up there but, It looks to be like 5 or 6 to me. Now, from where the edge of the roof starting all the layers have been worn away by the tree those couple inches going in a stair step look going from oldest shingle to the newest. It also looks to me like there is a layer or two of old wood shinles but, since the house is so old I don't know if that was some first layer technique that was used way back then. Now, my questions are 1) is it OK to try to repair the old "flashing" or get some new stuff that obviously won't have that tarnished green look. 2) Do I have to replace the shingles all the way to the roofs surface or can I just lay one or two down on the top While trying to have it all look correct. 3) How does one nail a shingle down without replacing shingles all the wat to the peak since they overlap eachother to cover the nails. 4) Can you buy single shingles?