I went and looked at it again today.  There is seriously _no_ rust
underneath, or in the tire wells.  Where there is rust: under _one_ of the
side windows - goes all along the bottom of the seal, and on the inside of
the sliding door - all along the inside of the very bottom lip. That's
pretty much it.  Are these real bad?  Can a sliding door be replaced?
 Seems like that would be a lot easier than any rust on the body itself.
 How bad is it to have rust underneath a window?

Also -  above the front seats there's like this cardboard, or thin
press-board, paneling .  It is kind of warped and I can push it up and
down.  Is this normal?  Otherwise, the inside looks great, barring a few
dings here and there.

 Thanks again, JJ