Hi Linda,

To question 1:  Yes, easily.  Cut around the edge of the foot with a
small sharp knife, and everything lifts right out.  The girdle will
still be intact.

2:  You don't really have to mark them.  After removing the foot and
viscera, lay the chiton on its back in bleach, in a flat-bottom
container.  The bleach will dissolve away the girdle and everything else
but the shell plates, and the plates will be lying on the bottom of the
container, in order.  Of course this assumes that the chiton was fairly
well flattened.  If the chiton is tightly rolled, the plates may not
line up as well.

Paul M.