A 'caliper' is the main body of the brake unit. ( it is NOT "on the tire") It carries the brake piston and mounts for the two disc pads. You may need new pads if they are worn , but unless your vehicle is quite old it's unlikely you need a new caliper. Get someone who knows about brakes to tell you.
No, you will need a new tire.
There are tread wear indicators that are in the tire itself. When the tires need to be repalced theese indicators show.
To change an actual tire you need a tire machine to get it off the rim and the new one on. -If you mean the change the WHEEL and tire on a car, then you just need a jack and a tire wrench.
there are several for sale on gunbroker.com and auctionarms.com you will need to know the maker and caliber of your stock to get a proper fit.
We would need to Know WHICH Saturn and make and size of tire. The pressure is the same whether they are new or old tires.
Yes I need the code
The date code is written on the sidewall of all tires. Click the link to my blog and scroll down to "New Tire Old Tire" where I explain how to tell the age of a tire.
To change a flat tire you need a jack, tire iron and a new tire. Jack the car up and remove the bolts, you can then slide the old tire off and replace it with the new one.
I inspect the tire and measure the tread depth.
If the new tire is within 4/32 of the others on the axle, and you're not putting a recap next to a virgin tire, there's really no need to.
uneven wear on your tire tells me that you dont rotate your tires and you probably need a new set of tires
If you bought new tires I would suggest you get an alignment also, this way you are ensuring the life of the tire. Plus some tire shops will not warranty the life of the tire if you have a bad alignment