Geez, maybe I should have posted here a week ago ... 

Later this morning, I suddenly received my refund
from Mandarake.  Took 2 weeks (after they received
the returned package and said they will be senidng
me the refund through paypal) and a number of
e-mails, but I finally got the refund from them. 
So, it is FINALLY over.

When looking back at this situation, I guess the
only thing I could have done differently is to
just trust my instincts, but I really don't know
how a thing like this could have been avoided.  I
did ask around and did ask the seller directly as
what many of the people I spoke to suggested.

Any suggestions or tips anyone can give?  I
remember someone telling me that they knew of a
couple of cel dealers who are experts on
determining if a cel is real or a reproduction
since they have a lot of experience in these kinds
of things.

Thanks again for the kind advice and help everyone
has given me.   :)