hopefully you can expect to find exterior grade sheathing : would it be reasonable for anyone w/no experience to come into your work & perform at your level of expertise ? think you already know the answer to that, right ? short answer's NO !
finish the siding w/same mtl for best results,,, downside is reside that whole side as your present siding may have faded over the years.
again, IF you decide to undertake the demo, be EXTREMELY careful,,, that wood cribbing up against the structure's there for a reason,,, falling rocks tend to flatten one's head & shoulders