John, door skins are relatively easy to replace. Grind along the edges of the doors until the outer skin separates from the shell, and use a wide, flat chisel to clean up the metal left on the inner side. The new skin is placed into position, and the edges are rolled and crimped around the shell edges.
Piece of cake for any decent body shop. I see that "B" skins are about $90 a side from VB.
Personally, I would strip the paint from the door to determine the extent of the rust, and maybe go with a patch. VB is also selling a patch panel for the lower door for 8 bucks. A bit more labor intensive to install, but cheaper, if you are doing the work yourself. If you are paying a shop to do it, it would probably be better to skin it.
Jeff