I assume that you have figured out how to do the quick job of replacing the shingles. The longer term problem is the water spot on the ceiling. I have had this problem before. Get a "spritzer" "spray" bottle and fill it with clorox. Be sure to cover he area below with something that will catch any drips or overspray. Then simply spray the affected area with the clorox. It will generally bleach out the stain. You may have to repeat the process a couple of times for full removal. I have found this to be quite effective. good luck. dale