If anything, the black interior will make it more difficult to sell. First,
you eliminate the buyer who does not like black, but is content with the
available color schemes common to the year van they are shopping. Second,
just how does the new owner find one of these rare, black panels, when the
time comes to replace one? It makes me wonder what condition the slider
panel is in. That one, specifically, is difficult to find in good
condition, in the usual colors, let alone a black one.
That is, of course, just my opinion. Black interior might be as rare as
balls on gnats.
I would price the van like any plain jane GL with a skin condition and get
on with it.
Good luck,
Miguel