I don't know Unix at all, but someone explained to me a simple way to do it. Load the playlist into foobar, hit CTRL-A to highlight all the songs, then Edit (tab) -Sort- and it gives you the option to reverse the playlist. Then just save it under foobar-I used the mu3 format there and used Playlist Creator 3 to reload the playlist and save it in the format I wanted. Great and simple solution.
BTW slimserver requires absolute playlists and somehow my drive letters changed (I think because I used my DVD drive recently) so I did load the playlist into my word processor and did a mass edit to change the drive letter.