Its easy to upgrade, just keep any config customizations in your user.config as discussed here.
Get the mojoportal-2-2-7-3-postgresqlreleasefiles-for-mono.zip. Copy all the files from the web folder into your webroot foder and visit /Setup/Default.aspx
No real reason to use the build service packages. Maybe the installer setup the apache and mono configuration and the database for you, but now that those things are already setup but nothing needs to change with that so upgrading is just getting the new files.
Hope it helps,