I replaced the east side of my house and garage after the shingles had been on 40 years. That's better than aluminum or vinyl siding is rated for. I used grey solid color exterior stain by Benjamin Moore and stained them front and back before installation. I had to use solid color as the house was stained barn red when I bought it,and I had already changed the color on the other shingles. Also because of the high humidity in MD, if we leave it natural, it blackens instead of turning that nice grey color.
The Cedar Shingle Institute in WA sent me some excellent information on installation techniques. Maybe they can help you with finishing questions too.