One thing you can do, if you're still not convinced, is give Corsair a call, explain it to them and see what they say.
If it were me, beside the smudges, if the rest of the case looked fine (overall construction, wires to the front panel, holes drilled properly for the standoffs, etc...), I'd just wipe out the smudges, and go with it.
I talked to Corsair tech support yesterday and they said it should be fine, and even if I got some of the smudges on my hands and touched my components, the residue would not be likely to cause a short. I'll give the inside of the case another swipe tonight with a damp towel and leave it at that.
Follow up question: does using rubbing alcohol (isopropanol) to clean the inside of my case cause any problems? I just used a bit on a q-tip to wipe up some of this residue.