I've spent some time and learned meshlab and blender a bit more and attempted to clean up this skull. Not a perfect job I'm sure, but better.
Being from a biomedical scan, the original had lots of internal details that are really cool to explore, but aren't too interesting when you're printing the object. I've removed all of the insides of the skull, and closed all the holes. (I never knew human heads had so many holes -- much more than the obvious 7, and all the ducts to go with them too.)
In particular, I had to close the eye sockets, the nose, some areas in the mouth, and the spinal column. All of these large closed holes left ugly scars, which I then smoothed in blender.
I think the result is better and should take about half the time to print, even though it is now solid instead of hollow. If it was actually hollow, it should take even less time to print.
I will eventually try to hollow this version out (without making it paper thin if I can) and slice it in half for easy printing, as was done with the original.
This is my first attempt at cleaning up a model like this. I could probably start over and do a better job in a fraction of the time with what I've learned, so criticism of this work (what did I miss?) would be appreciated.