Just out of interest, I have reskinned a '73 model (early) doorskin: Remove door (make note of what shims go where behind hinges, strip out main glass, and mask with cardboard 1/4 light (grinding/welding will etch into glass). Remove handle. Put door flat with frame down. Using linishing disk in mini-grinder, or gently with grinding disk, run around rear and bottom of door skin where it wraps around frame. Drill out spot welds on front edge, and cut cross braces on top of skin - frame, and right at top / rear of skin. The skin should peel off. Clean frame up and prime with high zinc weld thru. primer. Fit new skin over frame, spot or plug weld front edge just in a couple of places, plus tack cross braces at top. Using hammer and dolly gently take skin over frame, do not pinch right up. Re-fit door to car, at this point the whole door can be twisted through it's length to get perfect alignment. When spot on carefully and gently remove again, weld front edge and braces, and continue peening main edge over. Check alignment again, before final peening over. If all perfect put a few (4/5) tiny welds between rear of skin (the beaten over bit) and frame. These help stiffen the door - however you don't want to put any heat into the front of the skin or you will start a distortion. If unsure leave it as most cars aren't tacked here anyway. Then remove black protective paint, etch prime and paint as normal. Put in a couple of sound deadening pads, and cavity wax, re-fit glass and door mech.
The replacement skins are I think all galvanised (hence the etch primer). The one I got was aftermarket, and looked fine, but actually turned aout to be slightly rippled, so I ended up having to fair it in, although the actual panels gaps were fine.
In conclusion: by far the easier option is to get replacement door (take a magnet with you!), but if you've got a reliable welder, grinder and good quality hammer and dolly, it's quite DIY'able.
