I cleaned the corrector plate on my C8, it started off as a scary exercise but in the end it was straight forward and not too bad at all.
I don't know if you have a manual but here's a link for the Celestron manuals for quite a few models.
they are a great scope and mine is still offering wonderful views even after 32 years.
http://www.company7.com/library/celestron/notes.html