I'm repairing a shingle roof with a painted steel roof. I have the materials ordered and want to know about putting it on over the old shingles. So far I know about putting 1 x 4 boards horizonally every two feet and screwing the precut steel panels to them. What about installing the cap and drip end pieces, and flashings around two vent pipes and a 2' x 1' 9" roof vent fan?