Replacing damaged shingles
Fairly simple process.  Remove any and all damaged shingles so you are back to good firmly secured, making a block area to be replaced.  Start at the bottom, using exact same size/color shingles.  Put a few daps of blind roofing cement or roofing sealer (caulking tube type) along the old sealing tabs of the lowest existing shingles. (located just above the tab slots). Lay and nail the new shingles going up until you get to last course.  You will have to lift and pull the nails on the top border of existing shingles so you can insert the top of the new shingle under it and get a few nails in them. Now add a few more daps of sealer, lay the tabs down over your new shingles and replace the nails holding up the tabs of the next tier.  put a few daps of sealer and just lay the tabs back down.  Along the sides, you may have to do a few under slides, but use the same procedure as you would at the top.  Good Luck. BTW, shouldn't your homeowner's insurance be covering this fix, along with the interior damage?