I would advise against seperating the layers.  Of
course it really depends on the cel itself.  If
you are separating a layer of the mouth or eyes, I
think  it would give it a weird effect.  If it is
a background or effect layer it might be cool
though.  Like Chi said, I really think it is cool
when the cel is lifted from the background.


In my experience with framing, the more layers the
cel has, the harder it is to see through to the
background.  Also, if you seperate the layers, it
might cause or make small defects show.  Small
bends, oxidation, dust particles. When the cel is
up on the wall you can see it from all angles. 
Sometimes certain glares can hit it and show bends
(not creases).  Then again, it all depends on the
cel.  If you had a scan of it we might be able to
 provide better advice.  


If the person framing has experience in cels, it
might be worth it.  Keep in mind that a lot of
framers dont.  The first cels that I had framed
the person did a horrible job and it was very
expensive.  After the bad experiences, I purchased
a mat cutter and started to do it my self.  I
think that I achieve exactly what I am aiming for
this way.  It is actually suprisingly easy as
well.  Also, unlike others, (knock on wood) I have
never had a bad experience with line fading or
anything as long as they do not encounter direct
sunlight.  If you put the cel in a position to not
  encounter any sun and use UV protective glass,
it is a wonderful way to preserve a cel in my opinion.


Anyways, good luck!  I love framing cels.  It
makes the hobby so much more fun.  After all, what
 good do the cels do just sitting in your book.


 Ryan