Welcome to mojoPortal! I am sure you are going to love it!
When you add content to a mojoPortal site, that content is saved in the database. Any images, flash or other media are saved to the \data\sites\[site number]\ directory.
To upgrade a mojoPortal site, all you need to do is download the new release, unzip it and then copy it to your server. Once copied to your server, you open the http://www.yoursite.url/Setup/Default.aspx page in your browser and the database gets updated. It is a fairly painless and straightforward operation. I host dozens of mojoPortal sites and (with the help of a nifty script I wrote) I update all of them in minutes.
For the best results, you should become familiar with the Upgrade Documentation before attempting an upgrade.