Hi there and welcome to Android Forums and the world of Android!
I think being new to the Android OS is the factor, not the age. And I'm right behind you, like many others here.. lol
I personally don't think you should start with a lower end or entry level phone because most of those have lower end specs and that might sour your Android experience. Since the OS is going to be the same on different phones (some will have different release versions however), I would choose a phone with access to the newest version of Android so you have the latest and greatest.
The most important factor to consider is how will you use your phone? Are you a heavy web browser, heavy phone usage, texting, listening to music, watching movies, etc?
Things like a removable battery might be more important than user interface. Whichever one you start with will be easy to learn. I was a HTC fan until the last year - but it's my personal phone usage that has taken them out of my line up for choices.
Samsung Galaxy S3 is a good phone, you can't go wrong. They've lightened up their TouchWiz UI so what you might read from a year ago probably won't apply to TouchWiz anymore. Same for HTC Sense, actually. As mentioned above, Samsung will update their phones pretty quickly now, much faster than they used to... they're Numero Uno and their momentum is making waves in the Android world. No way they'll let that dwindle.
Once you get the basics, you can move on to more involved settings if you want, but you don't have to. That's why I say start with the best; then the choice is yours on how customized you want it.
The learning curve will be no different from phone to phone, IMO; and the posters above are correct - you can always visit here for any questions you might have. It is a REALLY great community!!
Good luck and let us know what you decide!
