I have a 25 year old 4 pitch metal roof in northrn NH. It has several (8-10) leaks and many old repairs. It totals about 20,000 sq ft. It was suggested that I use Topcoat to repair it instead of replacing it. Any opinions on the subject? How can I figure out how much it will cost. Is it something I can do myself? Do you have to be a licensed installer? Is it really going to last 20 years? Does it look like a new metal roof?