The calendar doesn't support widget based sidebars (yet). I haven't worked out how to create a widget yet.
For the installation, read part 1. It is to be installed in your WP root. The thread you read where the client was told to move the calendar's folder is because they had followed old instructions that said to install in the wp-content/plugins folder. It's not really an issue, it's just that you'd have to adjust the paths to work.
The one thing you have to make sure is that you _have_ to use the same database as your WP installation. No ifs, ands or buts.
As for the threads being closed, it's a measure that had to be put in place to limit the amount of SPAM that has to be dealt with. Threads are automatically closed after 30 days (I think) of inactivity. We read all of the threads and respond to everyone that ask a question... if they don't come back to confirm that the fix worked, or if they don't provide the information that we require for troubleshooting, we can't help it.
And about your other post, asking for part 3, it is in the works, but I've run into issues on my dev machine and haven't had the time to fix it to keep working on the tutorial. With a new house and undertaking my third $100K project in one year at my day job (Exchange 2003 to 2007 migration, LCS 2005 to OCS 2007 R2 migration, and now Exchange 2007 to 2010 migration), I'm sure you can understand that time is in short supply. If you're really interested in customizing that install, contact me using the link in my signature and we'll keep this going via email - that might give me the opportunity to finish off part 3.
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