Thanks so much. The plugin faq was misleading because it says
Can I customize the way the login and registration forms look?
Yes! There are three IDs available for customized CSS specifications – wpmem_login, wpmem_reg, and wpmem_msg.
So I thought they were divs with IDs, never even thought of them being classes.
Thanks again!
Never mind, the answer was staring me in the face! For anyone else who is blind like I apparently am, this can be done in the Plugin settings, under language. This page lets you change the text for all sorts of things, like the past event warning, no events to show, etc.