I have re-shingled several homes I have owned in the past. Not that difficult to figure out, but a lot of work.
A couple years ago, my house was in need of a new roof. The old shingles were coming apart, and it was time for repair before water damage started. Decided to contract it out since it was winter time, my roof has an extreme pitch, and I don't heal as fast as I used to when I fall off roofs.....I priced it with several contractors, and found a rather large difference in prices, so it pays to shop around. The prices between architectural shingles and metal was not that great. I like the look of shingles, but decided metal was going to be more long term durable.
It was $6200.00, installed over my existing shingles. It would have been more if the old shingles were removed, but I was advised to leave them on, since there was no damage under them, that they would provide increased insulating properties to the new roof. Building code allows for a new shingle roof over an old one, and a new metal roof is quite a bit lighter than shingle, so leaving the old one on made sense to me.
I was worried a metal roof might be louder in a rain storm, but that has not proven to be the case. I also ignored the contractors recommendation to install snow guards to break up sliding snow. I had him come back last year and install them, as the metal roof is slicker than shingle, and the snow and ice seems to slide down in big sheets otherwise. Heating costs are down some do to the better insulation. My only real complaint is snow, instead of sitting on the roof, tends to slide right off. I have a full length deck on both sides of the house, so have to do a lot more shoveling. Overall, I think metal is a more practical material choice.
Larry