Low grade stainless steel screws and nails will sometimes stain the surrounding wood.
A plugged or blocked chimney could cause the products of combustion to back up and filter through your home…and that is very dangerous to your health. So inspect your chimney each fall. It’s simple and only takes a few minutes of your time.
Get at least three written estimates from contractors who have come to your home to evaluate what needs to be done. Be sure the estimates are based on the same work so that you can make meaningful comparisons.