1205 Door Restraining Strap

Newbie here who posted the same question on the Packard Club fourm before becoming aware of this site. I'm looking at a 1935 1205 convertible sedan with the driver's side rear door retaining strap broken. Picture attached showing a piece of the strap sticking out of the center B pillar. How does one fix this? Must the B pillar and rear door upholstery panel and front seat be removed to get this done. How hard is it to do and is it a very time consuming task? Glen