Have you had a look at the webcalendar faq at http://www.k5n.us/webcalendar.php?topic=FAQ#faq_18
Item 1 of the FAQ you can ignore unless you have installed your own PHP.
Make sure you have setup the cron job which reads your calendar events and sets up the email reply.
Have a look at wiki.dreamhost.com when it is working again to see how to set up a crontab.
A line in your crontab file similar to :-
1,11,21,31,41,51 * * * * /usr/local/bin/php /home/USERNAME/calendar.example.net/tools/send_reminders.php >/dev/null 2>&1
would be useful.
You should enter your own username and change the calendar.example.net for your calendar folder.
The line is one single line and when entered you should make sure it has a blank line beneath it if it is the last crontab entry. i.e. press the enter key twice at the end of the line.
Before sending email reminders to your gmail account I would first recommend using a valid working dreamhost email address.
Opinions are my own views, not DreamHosts'.
I am NOT a DreamHost employee OK!! :@
You act on my advice at your own risk!