local dir replace, incoming dir edit upon update?

I guess that running the update through Wordpress deleted the .svn folders that were present in the plugin (the needed stuff for SVN to work properly).

So you could delete the new, unversioned eventON folder that you have copied in your repo, and run a svn update from one directory above (wp-content/plugins), in order to retrieve the old, versioned plugin.

If it does not work, it may be easier to delete the repository and checkout a fresh version...

Then, you will be able to update your plugin manually through SVN, and commit it.

As long as you already know that you want the server's version and not the local, this shouldn't be too difficult to resolve.

1. Identify which files are conflicted with svn status.
2. Since you want to keep the repository's version, you probably want to remove any conflicted files that svn has added from your working copy. They will have an A next to them in the output of svn status. In your case you should probably back them up first, since svn can't get them back for you since they're not in the repo yet. Now use svn delete --force my/fileToDelete. You don't need to delete anything not related to the tree conflict if you have made other changes you want to keep.
3. Run svn resolve --accept=working my/treeConflictFolder on the remaining folder that is conflicted (it will have a capital C next to it in the output of svn status)

The tree conflict should now be resolved, so you should be able to commit and update normally.

Further reading: http://svnbook.red-bean.com/nightly/en/svn.tour.treeconflicts.html