Is it diffulcult to get days off in advance? Lets say for example you played in a softball league in the summer and you needed Friday nights off for a couple of months. Would that be a problem?
depending on what shift you work you won't have to worry. if you work the twilight sort (5-10pm...usually 11 @ my hub) you're going to run into problems. However the night sort starts at 11 (again here at my hub) so that probably wouldn't affect you (you'd just have to work after your game). If you worked the Preload shift you'd already be done for the day, which is one of the few bright spots about that shift (I work on the preload).
however your original question, at my hub its not hard to get days off, tell them when you need them (if you're using a personal day) and they'll let you know. If they don't give it to you theres always using a sick day (just call in and tell them you won't be in). I can't say this enough though if you're going to miss work CALL them. Less headaches and besides once you've been here a bit why wouldn't you? you get paid for it if you call.
Then again, you will be new (judging by your other thread) and won't have these "luxuries" when you start so I'm not sure what you'll be able to do except pick your shift (if the opportunity is there to do so) accordingly.