Well. . .I'm no expert, but my ex was a painting contractor. I would say go with an established company. That way if you have problems later they will still be around and willing to rectify the problem. When we needed a new roof, my ex decided he could do it himself. Like the poster above, we only had one layer of shingles, so no tear off was necessary. This can save a lot. . .less labor. . no dumpster and haul away. I think you can have up to three layers of shingles before you have to tear down. . .but don't quote me on that. Also, ask about scheduling. . .some contractors are notorious for starting a job. . .then starting and working on another, meanwhile your yard is a mess, etc. As far as shingle quality. . .pick the best quality you can afford. We have regular asphalt shingles, but the new composite ones are suppose to be very good. . .30-50 yr lifespan. Just research what you decide to go with. I'm not sure how composite goes on. . .so tear down might be required.