The biggest issue will be any bad side wall framing, top sill rot, and roof trusses that are beyond usability. Be forewarned, if leaks are allowed to go unchecked, there will be frame damage that is not visible until the user starts ripping into things.
This kind of repair work is just basic carpentry, not at all beyond what most guys can tackle. A few of the most problematic aspects are removing fasteners that were installed in a different schedule than what you'd like to have (staples and screws underneath siding and floor), removing interior fixtures if necessary, and achieving a square and plumb installation of new lumber (the framework moves out of square and plumb as it rots and settles).
Good luck with the repairs! You can check out the link in my signature line to see how I dealt with a full restoration. Also, when repairs have been done and all is sealed, complete a pressurized leak test to make sure there are no existing leaks.