In Ray's case I would definitely employ somebody who knows what they are doing, to do it for him.
Those "prefabricated triangular wooden roof sections which face front to back" are pre stressed roof trusses.
Your walls are load bearing, those trusses are holding a lot of weight, figured out by structural engineers taking into account things like snow loads, wind factors, ground heave etc.
The piers that are built into walls have pad-stones or lintels and so forth to spread the load, making a hole in the wall could put stress in areas that are already stressed and not only from above.
