Thanks for the quick replies, steam cleaning is a great idea. I have a
friend with a mini steam cleaner which would be perfect to use in the
cabin. 409 is pretty much what I'd tried originally, and apparently
that was a bad idea? I'll take a look at oxiclean products, and some
hard scrubbing might help regardless. I won't be trying to replace
that headliner by myself anytime soon--while I love projects, I hate
blunders.

Thanks all,
Mike