For both, you're likely talking customization of the portal/resources files
that govern the display of the documents  in the list. Out of the box or
with a GUI answer, this is not a function of SPS.

Ahh. Just found the link that should point you in the right direction:
http://www.spsfaq.com/customising.asp?postid=654

You might be able to add a kind of "don't display this file  if the filename
ends in .dat" rule, as well as some wording that will use a different
attribute and, even better, another option in the header, to sort  by other
criteria and field names.