Yep - I've 3 sites now running on Joomla - took me about 8 months to get my head around it all, but once I'd got one site sorted, the rest weren't too bad. Worst was the FMSNI site though as it had 100 pages + all of which had to be weeded out and cut back, plus I'd a lot of problems with the database corrupting and various other difficulties - steep learning curve, but trust me, if I could do it, anyone could!! I chose Joomla out of all of the various CMS offereings because it had the nicest administration and a absolute bucketload of templates and mods/coms to play with unlike some of the others that (for me at least) seemed rather limited unless you were experienced.
Joomla also has a superb forum where you can get fairly quick help on any likely problem you run into, plus they have good documentation that's easy to work through. I'd highly recommend it as a platform for anyone starting out in CMS. You can get a great idea of what it's like to manage if you head to
Joomla Demo on the CMS demos site - you can try out all the others there too. Gives you at least an idea of what you'll see once you install any of them. For me, it was far harder to get my head around the actual PHP database and I'm still learning on that one - you have to take regular backups through your CPanel/PHPMyAdmin regularly or you can end up having to lose everything and reinstall, and it's something I've not found anywhere you can really easily learn what's required - really is just diving in, messing it up, and then playing around to fix it (with a LOT of help from forum friends). i've killed 1 of my sites twice over just through doing silly things sometimes, so you do have to be really careful, because unlike with your HTML sites, you won't have any means of accessing information to put it back up again if your database gets totally corrupted, hence the regular backups.
I'd be more than willing to help you out should you ever need it tho I'm sure you're more than capable of undertaking it as I'd zilch knowledge when I started out with it, and had no idea what it would be like until I set it up and just dived in learning as I went.
Thanks for the encouragement tho - nice when the work is noticed