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You have more then one problem here in my eyes. It looks like you have some sheetmetal adventures coming your way. Trying to find a replacement door is going to be difficult. The good news is, is that it is repairable if you chose to go on that adventure. Here's what I see besides the cracked frame which can be either welded or repair doublers riveted internally. The hinge needs to be checked of elongation of the hinge pin holes. These can be bushed by a competent machine shop. Lastly it looks like the exterior skin is to warped/damaged to reuse but it can be used as a template for a new one. Know here's one other issue, the door should be repaired with the trailer present in order to check the contours fits and clearances during the repair process. The sequence should be this, 1) remove door and hinge, 2) deskin door interior and exterior, 3) repair hinge, 4) reinstall repaired door hinge and door frame, 5) restore door countour and repair cracks, 6) fit exterior door skin with the frame attached to the trailer, this will help maintaine the correct contour, 7) rivet exterior door skin on, 8) fit interior door skin. Riveting on the interior door skin will lock the contour in place and make the door ridged again.
This is not for the light hearted but it can be done as I have already done this. check out my thread below starting with post number 231.