Hi. There are a number of Perl modules that can be used to simplify the sending of e-mails - Email::Simple, Email::Sender::Simple, etc.. The HTML::Template module can be used to generate the HTML, and - if you need attachments - the Email::Stuffer module might help.
Is SMTP already configured on your server (e.g., using the Exim4 package)?
If it is, then the process should not take long. I can provide a sample Perl script which you can call from the command line with a list of names/e-mails and a template message.
I am based in Ireland - so operate in GMT (about 12 hours difference from Australia).