The following PDF files make "good reading" for someone considering installing or purchasing metal roofing. One needs to read all of them as some are somewhat "abbreviated" and lacking some important details...but reading all of them will cover about everything:
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http://www.unioncorrugating.com/pages/installation.html
Figure'd that I'd post up a newer (functioning) link for additional materials that I've come accross:
http://www.bestbuymetals.com/how-to-install-metal-roofing.html
Some really great material that is pretty straight forward while also being "in depth".