First, I want to thank everybody who is trying to help a noob such as myself with this problem. You guys are great.
To answer Brett's question, JEdit is 4.3.2. LilyPondTool is 2.12.894.
Below, I copy a note I sent off-list to another potential savior explaining the latest problem. If anybody on the list can help me with this and help me get the freaking program going, I would be eternally grateful.
James Bailey said he uses the command line. James, I assume you can do that in Snow Leopard? The only reason I've been trying to run LilyPond with JEdit and LilyPondTool is that a friend of mine uses that combination (albeit from a Vista installation), and he loves the way he gets instant feedback on what his code actually looks like. I'd like to do that if I can. Do you find that you can get a visual confirmation of what you're doing via the command line frequently enough for what you need?
Oh, the other reason I developed this workflow was because at the time, lilypondtool didn't exist, the lilypond editor became woefully inadequate and the texshop solution was frustrating in its lack of tools. Also, while it does require much reading, so does lilypond, and so we're clear, lilypond was the very first thing I tried to run in the command line, before that, I had no idea. A year or two later, I was writing my own syntax hilighting definitions for nano! I say that to say that even a noob can learn it.