Need to remove the door latch mechanism from a replacement door I just purchased. When the door handle is turned fully to open (down), the latching mechanism does not retract fully and the door will not open. It will open with the interior latch release.

What’s the best approach to taking apart the door? I’ve already removed the inside window frame and triangle window with it. Do I have to remove the glass for easy access to the door latch mechanism?

My old door bottoms are rotted inside and out, but the window crank and door latching mechanisms works well. The new door I got is in much better condition at the bottom, but the latching mechanism does not work well and the outside door handle actually sits at about a 45 degree as opposed to horizontal.