Reuben,
I repaired my door quite a few years ago, so I am relying on memory (scary thought
) for the repair. If I can do it, anybody can.
With the door off and laying interior side up, remove (unscrew) the metal frame strips. Remove the window trim pieces and remove the glass. With a metal paint scraper, gently remove the interior metal door panel. It is glued on. Now you are looking at the wooden door frame. The center section of the door consists of a piece of styrofoam that the window sits in. The bottom piece is a 2x6 piece of wood and the sides are 2x2's. The top of the frame work consists of 3 pieces of wood, mitered together to form the curve in the top of the door. I used treated lumber to replace the original wood. Use the original wood to get your measurements for the new wood. I reused the top 3 pieces as they were not rotted.
One of the 2x2's will have to be drilled to accommodate the locking mechanism. The new 2x6 is slightly thicker than the original bottom piece. It will have to be sanded or planed down for proper thickness. I used PL400 construction adhesive to reglue the interior metal panel back on. Also used new stainless screws in the reassembly of the door. Unfortunately, I did not take pictures when I did this repair. Hind sight is always 20-20. Your door might be slightly different than mine, but this should get you started. Good luck with your endeavor.
Bob