Since I'm not Army, take this with a grain of salt. From what I remember from these boards and such, Army got their commissioning paperwork more than a day or two before hand. What people were doing was taking their orders to a base, using that to get on, then obtaining an ID and buying uniforms. However, yes, this does require you to have the paperwork prior to leaving for OBLC.
I'm sure you can get commissioned at Ft. Sam. The year before me, the Navy didn't get the commissioning paperwork and orders out to people until the Friday before they were supposed to be at ODS (you have to get to ODS by noon Sunday). This lead to last minute flights and they all were commissioned at Newport. For us, they got the paperwork out about a week and a half before ODS, and if I remember correctly Army got theirs before we did. Navy is the slacker in this regard - Army and AF tend to get them earlier 🙄
That said, I know you're super excited about acceptance (I would be/was too), but it's only November. Don't worry so much about all this. In reality, it'll all happen about a month before you leave, and while a plan is good, you don't need to figure it all out now 😉