Thanks stevehero. I was hoping for something that does both the filename and the tags at the same time, but I'm not averse to using two separate actions if that's how it needs to be done. I gave your 2nd "_Script Test#TEST" example a try, and it still changed "04 - W.A.S.P.mp3" to "04 - W.a.s.p.mp3".
In the time between my post and your response, I came across this thread, and managed to successfully create the following action:
Action: Replace with regular expression
Field: _ALL
Regular expression: ([^,]*)
Replace matches with: $caps2($1)
[ ] case-sensitive comparison
This actually works very well, but has a flaw. If a bracket is used and not closed, as in "04 - Chub (A Lub.mp3", the filename and title will be changed to [ SYNTAX ERROR IN FORMATTING STRING ]. The rest of the action scripts in that thread aren't really fully explained as far as what they do. It don't think I could dedicate enough time to figure out what those long character strings actually mean.