You will have to pull a lot of inner skin to repair this. The ribs are extruded similar to a double "L" with the leg at top and bottom going opposite directions. You could use 2 pieces of angle on opposite sides of the crack.
I would seal the window from the inside, make a piece that fits the opening and rivet it in place with some sealer between the 2 pieces. I had to do this with the driver's window on my motor home, the opening had been cut 1/8" past the frame.
If the door frame is extruded it can be bent back into shape using a 2x4 to leverage against, no need to cut and weld. You may need to loosen the skins, and don't push agains them.
Unless this is a real deal and you don't mind the work I would think seriously before buying. Pulling cabinetry and skins is a lot of work.