Shawn
You've been having a run of bad luck, haven't you? Well, before anything else, I'd say that I wouldn't use CMS yet. It has a terrible UI, although it does have a very good data model, at least from what I've heard. There are some other efforts going on to build a better user experience on top of much of the CMS's core.
Have you done anything that you want to keep in the database? If not, the easiest thing to do is to drop the database, and restart it, with a new installation.
I think there is a document somewhere which shows the list of supported applications.
But to answer your question: to clean it out,
If the package is written well, you can clean it out through the admin UI
If not, then you may have to do portions of it manually.
What I'd suggest is getting on IRC and asking as you encounter your problems. You'd probably get better help there, and in real time. Info on that is at https://openacs.org/irc
We know this is very annoying, but things are improving very quickly. There are a lot of people working very hard right now to make this whole experience seemless.
