Thanks. I found that page myself a few minutes after I posted here!
Realizing that, based on your own admission, you are not the best person to ask this, I hoping someone else will read this, or you can take a stab at it again, you were right on last time
I added both lines:
$ScriptUrl = 'http://'.$SERVER['HTTPHOST'].$SERVER['SCRIPTNAME'];
$ScriptUrl = 'http://'.$SERVER['HTTPHOST'].$SERVER['PHPSELF'];
Which by itself is a little wierd, because they're both to the $ScriptUrl variable. Viewing and even editing worked, but I'm not able to use pmwiki's skins facility because another variable needs to be defined according the sample-config.php file, $PubDirUrl.
But I don't know what path it's looking for. I tried the obvious http://www.domain.com/pathtopmwiki/pathtopub and that didn't work.