Procuring cider juice is an acceptable excuse for getting to work late. Just make sure to share some of the end product with your boss.
You are fortunate to have a choice of juice in one place. Taste em all and see what you like. When you are evaluating a juice mix for fermenting, you want to pay attention to at least four dimensions. First the smell if it doesnt smell good before the ferment, its not likely to get better. Then the first hit of the taste, which should be appley and sweet. The initial sugar taste should fade out fairly quickly and not be syrupy. The midrange is harder to describe, but want a nice flavor when its sitting in your mouth preferably multiple flavors.- something that remind you of biting into an apple in an orchard (as opposed to drinking a juice box when you were a kid). Then you have the finish, where a tart note is nice as long as not too tart.
It doesnt hurt to let them know that you are looking to make hard cider. Most apple growers also make hard cider and have their favorite juice combos for that so if you are lucky and treat them right, they might bring you some of the Good Stuff next week..
Here is the quickest, cheapest way to make a small batch:
Get a gallon of whatever you like the best, or two if you cant decide. Preferably unpasteurized or UV pasteurized - not heat pasteurized or with any preservatives. Dont heat the juice or add anything but yeast. Keep the jugs cool and dont open them until you are ready to add the yeast. If you refrigerate them, let them come up to room temp for about an hour before pitching the yeast. Since you like a sweet cider, use ale yeast preferably S04 or Nottingham. One packet is enough for 5 gal, but it wont hurt to over pitch the yeast. Pour off about 4oz of juice, and pitch the yeast, a little bit at a time. Let it sit on top of the cider for about 10 min, until it sinks, then add some more. Do this three times, then put the original jug top back on, give it a good shake and replace the jug top with a fermentation lock and 6 ½ stopper, which you can pick up when you get the yeast.
You should see fermentation start within 24 hours, usually a lot earlier. Let it set in the coolest part of your house. When the ferment starts to slow down (between 5 and 9 days, depending on temp), start checking for taste. You can pour a little bit out but its better to use a wine thief so you dont disturb the sediment. When you are happy with the taste, rack it into a clean gallon jug and stick it in the fridge for a couple of days to chill the yeast out. Rack it one more time into bottles or a pitcher and its good to drink. This way, you are arresting the secondary fermentation which is where the more complex sugars break down and you're not adding anything that might alter the flavor of the apples and yeast, which will still be very fresh. Its like a Beaujolais cider. You can wait a few more weeks to let it clear out if you want, but IMHO there is no need to (and often good reasons NOT to will come along).
Once you have this method down, there are a lot of ways to branch out, and as it gets later in the Fall, you should be able to get better quality juice at your farmers market
cheers