Umm. I think you might be surprised by how easy it will be.
Seriously.....Once you buy tires, there is nothing on a Schwinn that isn't something you can't buy at your local bike shop. They may have to order some things as the demand isn't there anymore.
And tires are easy to find on the internet, once you figure out what size you really need. Sheldon brown has a great page explaining tire sizes and how Schwinn tire sizes relate.
Here's hi page about Schwinn in general:
http://sheldonbrown.com/chicago-schwinns.html
Here's a supplier:
https://www.biketiresdirect.com/older-26-inch-tire-sizes-article
Sure, you won't walk in to Wally world and buy the exact right thing right off...but you won't find parts for the Wally world bikes on the shelf anywhere either. If you are looking only to get your parts off other bikes in the boneyard..ya gotta have the right bikes in the boneyard.
Maintenance and "upkeep" on a Chicago built Schwinn:
1: Keep it in a dry place and not in the river or salt mine.
2: Fix the tires when they get flats. Buy new ones when you can see the tubes through the sidewalls.
3: Once a year, lube and grease everything. If you skip a decade or two, it probably won't be noticeable.
4:Adjust cables when needed, replace brake pads if wiped out.
I saw a youtube video on the T&C Schwinn but didn't watch it.. it might help ya out.
Another:
I was "maintaining" my Schwinn 3 speed in third grade. 98 percent of my wrenching was adjusting the seat.
Refurbishing and restoring a Schwinn is pretty easy too. If you can "flip" a bike you should be able to work on a Schwinn. It isn't anything magic or really complex.
The name alone is what sells the new "Pacific" garbage called Schwinn...and 50 years from now I doubt folks will have the same love for them as they have for 50 year old Schwinn products today. (If there are any left!)