There is a place in California that has been 
doing cel restoration for 20 years or so.  The 
man who runs it has over 10 years of experience 
in dealing directly with asian animation houses, 
and knows about the problems with the art and 
lines.  They can fix pretty much any problem you 
may have, but...it does take a very long time if 
the damage is extensive.  If you email them and 
ask for the packet, you will receive all the info 
in the mail.  :)  Good luck!

http://www.srlabs.com/