OK, I tried logging in with the wp-admin link but still get a 500 error. I am new at this so maybe you could answer a basic question: When I install or update a plugin does it change any other part of wordpress or just the plugin folder itself?
While certainly I could have a problem "somewhere else" I think it is most likely that the plugin caused it because it happened immediately after I had updated updraftplus.
If plugins do not change anything other than the plugin folder then I want to try disabling all my plugins via ftp and see if that works before trying to restore my entire site.