What seems to happen is you can't open the door from a crashed C-47 to let the troops out.
Most goon runners will open the door prior to landing, that way, if you do crack up on landing, you an usually still get the troops out the door.
As to distance, I've see troops run quite a ways to a maproom. Even dropped troops behind trees near a base to have them run in. My guess is 800 to 1 mile distance to the maproom is the limit, but, I've never tried it.