I'm 60, my bike is 32, and my commute was 8 miles each way. I find upright to be quite safe because I can easily see what's going on around me.
Old mountain bikes make great commuters; they can take anything you can throw at them and carry all your stuff, and since they're not the new hotness they're less attractive to professional thieves. The Princess is sporting Velo-Orange's
Tourist Bar, which is about perfect for me; there's enough sweep to put your wrists in a neutral position and it's wide enough that my knees go inside the bar, not into it.
I recommend learning to do your own basic maintenance; on YouTube RJ the Bike Guy and Park Tools cover pretty much everything. If you have a bike co-op nearby they can teach you. And remember; however much you put into your bike it's still cheaper than a car.
You can also hang out on Bike Forums and learn a ton, especially in the Classic & Vintage (C&V) forum. Ask the dumb questions, admire others' bikes, and when you reach 10 posts, show us your bike!
Getting ready to start the Critical Mass ride.