This is a great example of why you want to hire a professional licensed and insured roofing contractor.
Yes like most trade professionals you can ask friends and family to help you get the job done. You might even save some money. . . . Well at least at first. However, you might run into some problems if you, your friends and family don't are know what they are doing.
proper placement of nails and proper roof ventilation, and a good sheeting, are a few things that help maximize shingle life.