OpenFace Systems, Inc. is the corporate persona of Ivey Brent Laminack. Ivey to my wife, Brent to most others. I've been doing database and web development for about three decades in and around Atlanta.
Joomla is a popular open-source content management system. It makes updating content on your website easy. Other open source CMSs are Wordpress (which runs many blogs) and Drupal (which runs many high-end websites like Whitehouse.gov). Joomla's the middle ground: powerful enough to do what you need done, yet simple enough so you can do it.
Past experience says if you're halfway computer savvy, yes. In the past, probably 80-90% of my clients have done 80-90% of their website updates themselves. The exception being things you only do once or twice a year. Yes, I could train you on it, but by the time you needed to do it again, you'd have forgotten. My team's there for you for the 10% that you're not comfortable with doing yourself.
Yes, you can get hosting for as little as $2.99 a month. You'll be on a server with over a thousand other websites and thus will get about 1/1000th of a person's support. Yes, you can get cheaper, but it's never worth it. It's penny wise and pound foolish as the British would say. On my hosts I have all the tools installed that I need to manage and maintain your site. Also, let's talk backup and site speed. Is your site really being backed up? When was the last time it was tested? I thought so. As to speed, this site currently scores 93 out of 100 on Yahoo's YSlow speed test. How fast is yours?
No, and neither can he. Anytime anybody guarantees you #1 placement for anything other than your own domain name (which you're already #1 for, anyway) run, don't walk away. No, I can't guarantee top search engine rankings for any arbitrary keyword, I can work with you to maximize the efficacy of your search engine marketing efforts.
Even though most of the people writing Joomla and other open source software don't get paid for it, there's still money to be made in support, customization, implementation, graphics, etc. So lots of people are making money around it. Joomla has a healthy ecosystem around the software that feeds the developers and keeps pushing the project forward.