Worst door Ive ever seen?
But totally repairable!
I dont have the link handy but something like
"You can repair fiberglass"
It was just mentioned in a thread in the last week or so.
As far as procedure, I would get the exterior panel rebuilt to shape.
Then shape the missing interior panel with foam cover the area with plastic or similiar and glass over. When cured remove new panel and foam, glass the new panel in place.
Yes over simplified but I type with one finger! Lol
The pics in this post might help you understand the process
even though the project is unrelated.