Plugin activation error causing WP Admin failure.

I have two problems:

1. On activating the plugin I get the error message "Fatal error: Class 'BP_Group_Extension' not found in /home/s1008356/public_html/wp-content/plugins/bp-group-calendar/groupcalendar/bp-group-calendar.php on line 103". How do I resolve this?

2. Site and WP Admin is no longer available. Is it the best approach to delete the BuddyPress Group Calendar plugin using FileZilla and then reinstall the plugin (once I learn howto fix problem #1)?

Thanks ... Michael