Gutter installation cost

I have a detached garage in Mountain View, CA built in 1962. The first roof was wood shingles over skip sheathing. Composite shingles were layed over that a long time ago and now it's time to redo it. I plan to strip all the old shingles, but probably keep the skip sheathing and lay 1/2 decking over them, and then a conventional composite shingle installation. The building gets very hot in the summer. It has no ventilation up high at all. I'd like to add rigid foam board insulation on the underside of the rafters, put vents into the eaves, and put a ridge vent onto the top. I’m hoping that will keep good airflow (due to convection) under the roofing (helping to keep it long-lasting), but also keep some of the heat out of the garage itself, while still allowing me to use my overhead storage space. Am I on the right track with this? If the rest of the space is still too hot, I would likely add a thermostatically controlled gable-end vent. -- Rich

My celing has been leeking on the back edge of my house for the past two years now. I thought it was my crappy roof that was on there, so I replaced it and my chimney this past summer. I went overkill on all the flashing and rubberized undercoating thinking that the water was coming through my shingles. I put a nice ridge vent on the entire house and added baffles and everything to get it nice and ventalated like it should be. This winter it started leaking again just as bad if not worse than last year. I thought maybe it was my gutters, so I siloconed them to the facial and all around each nail hole. So far no luck. My ceiling plaster can not take much more water before it starts to need to be replaced so PLEASE HELP!!! I honestly have no idea what else to do. I have a one story straight ranch with a shallow 4-12 pitch roof. All the wind and rain comes from that side of the house about 90% of the time. It also seems to be worse When it is below freezing and windy outside. I live in Michigan. Any ideas are GREATLY appreciated. Thanks all!