qclabrat

Great to see you are trying to work it out yourself, I always encourage riders to be able to do basic maintenance, cause it will save you one day when a few miles from home.
Make sure you don't send the derailleur into the spokes by adjusting the limiter screw too much. There are a ton of videos out there. I particularly like the ones which Park Tools puts out.

As for brake pads they usually have generic ones available at the big box stores but for rim brakes I like to recommend the Kool Stop Salmon colored pads are very good.
https://www.amazon.com/Kool-Stop-Can...s%2C230&sr=8-7

make sure they are for cantilever brakes and don't get the "thin" ones. They cost a little more, but not much better out there.

qclabrat

Also check the tires for dry rot, the Tioga tires I had was cracking pretty badly after about 10 years, I didn't ride the Aquila much back then and really didn't get into mtb till 5 years ago.
yours look okay, but can be sure with the pictures