Sounds bad.
Call Apple and make a complaint about this "black gunk."
I keep a binder for the complaints about the Macs. It may not be a big deal now but it might be useful in the future. Keep the binder and make a record of the date you called, whom you spoke to, where they are, and the case number.
Example: We received a G4 550Mhz Powerbook that had extremely tight hinges. Called and complained about it and Apple said it was "normal." A month later the right hinge snaps completely off at the bezel. Called Apple to complain and while talking to them the LCD twists slightly and the left hinge snaps also. Apple probably wouldn't have covered this damage and would have blamed it on our usage...
Except for a little case number recorded that discusses how tight the hinges are.
Apple completely replaced that Powerbook with a new and updated model.
Good luck.