New Roof - DIY Tear Off

[Adam Smith]

I just bought a house that will need a new roof within the next couple of years.  I also need to replace/repair the gutters, and of course, the siding needs work and a paint job.  I want to get the roof and gutters done first, then move on to the siding.   In college I worked for a roofing company for a summer doing the grunt work and tearing off.  I'm wondering if I could save some money by doing the tear off myself and letting a professional roofer complete the job.  Has anyone done this before?  Any tips for finding a contractor that would work with me?  I can see potential problems with timing (I'll be slow, roof could be open for several days etc.), and also I'm not sure I would save any money if I need to buy or rent all the tools and equipment.  Just wondering if anyone had any thoughts on how this could be done.