There's some general information on the internet, 
but all relating to western cels (I'm not sure
if there's a huge difference). There's no 
information on actual process, of course, and I 
have a feeling that no one with true professional
expertise would want to inform the rest of us on
what they do exactly.... O_o I believe there are 
amateur individuals out there who will do small 
restoration projects, but I'm not sure the depth
of that process is something a 'guide' should be
made out of, at least without a disclaimer...
^_^' Another issue that would work well in an 
informal guide is unsticking pencils and possibly 
layers, since I think that's something many people 
would be interested in.

Full restoration is for the rare, expensive, 
"valuable" cels, and can run up quite a bill if 
you're not careful.. Unless you want to go the 
amateur route, I know there are people here who 
would be willing to do that ^_^. *shrug* Merely
line correction is something common enough that I 
think it could warrant a guide in itself. :P