Thank you so much for your help. Here's the rundown:
Apparently my local installation of Python 2.3 wasn't working entirely correctly or something. I ran that Python test script that you linked up, and while I could execute it from the command line with python2.3, I could never get it to run from the browser. So, for now, I went back to the older versions of Python.
So, I did a completely new install, following your updated instructions. All was well until I tried the moin.cgi?test and was getting an Internal Server Error again. I tracked it down in the error logs to something about "False" not being defined. I had previously seen this mentioned on this page: http://moinmoin.wikiwikiweb.de/MoinMoinQuestions and since the default Python is 2.1.3, that was obviously my problem.
Next, I thought I might see if I could tweak the setup of my Python2.3 install. However, I revisited this page: https://panel.dreamhost.com/kbase/index.cgi?area=2434&keyword=python
and noticed that the "User Post" from 2003-03-06 also mentions that Python2.2 is installed and can be specified. (I wonder if 2.3 is also setup this way, I'll have to check that later).
So, I went back to moin.cgi, changed the top line to add python2.2, then I went to run the test, and for the first time ever I saw the results of moin.cgi?test. Everything checks out OK, except it says that some log file is not writable, but when I look for it in my folders, I can't even find it. I can make changes, and they're recorded, so it looks like this install is successful.
So, as of now, I have Moin 1.2.3 running with Python2.2.
Thanks again so much for your help.
Now off to changing URLs and customizing the CSS of MoinMoin...