Installing a message que system is completely optional. If you don't install one, the tasks run from cron as configured in your standard install will do the same work eventually anyway.
Installing a message que simply means that in certain important places, work will happen instantly instead of after a delay.
For example, when a user adds a new import the import will be processed and the user can see the results straight away. If you don't have a message que it will happen after a delay.
To use Beanstalkd, simply configure the options:
$CONFIG->useBeanstalkd = true;
$CONFIG->beanstalkdHost = 'localhost';
$CONFIG->beanstalkdPort = 11300;
$CONFIG->beanstalkdTube = 'openacalendar';
Simply run
php core/cli/runMessageQueConsumer.php
Note each worker will die after a certain amount of time, as configured by 'messageQueConsumerProcessRunsForSeconds'. You should regularly start a new one using cron to replace the one that has died.
This is simply a way to control memory usage in long running processes, by making sure the process stops and starts again with a clean footprint regularly.
Before upgrading, stop any existing running message que consumers.
Make sure to restart some new ones after upgrading.